How Do I Fix My Burglar Alarm? — Top Tips

Updated on March 10, 2018
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Eugene is a qualified control/instrumentation engineer Bsc (Eng) and has worked as a developer of electronics & software for SCADA systems.


How to Mend It - False Alarms

A blaring sounder on a security alarm is both annoying for you and those who live nearby. If you have good neighbors, they may keep an eye out for activity in the vicinity of your home when the alarm sounds. However If false alarms occur regularly, it can be like a scenario from the story "the boy who cried wolf" and they may just ignore it!
This hub explains the basics of how alarms work and how sensors are wired. It also covers the various faults which occur in sensors resulting in nuisance activation of your alarm.

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What Causes False Alarms?

  • Loose connections
  • Loop resistance resistance outside the specified limits
  • A worn out battery
  • Rodents, birds, bats or other small animals may be triggering sensors, especially in lofts or outbuildings
  • Tamper strips on junction boxes may be tarnished and causing bad connections
  • Tampers on some sensors are badly designed and may only barely close the tamper switch in the sensor when the lid is replaced. Consider replacing the sensor

How Does a Burglar Alarm System Work?

Alarm systems for homes consist of an alarm panel with a display and keypad to which sensors are wired. Alternatively sensors may be wired to a control panel box which is hidden away out of reach of burglars, so that it can't be tampered with. The user then interacts with this box via a keypad mounted on a wall. A microcontroller (which is a type of microprocessor) on the circuit board in the alarm panel runs a software program which scans the sensors regularly. The program will generate an alarm if it thinks a sensor has been activated and an intruder has entered the building.

Block Diagram of a Basic Security Alarm System

A basic 3 zone alarm system. 1 or more sensors are connected in series to each zone
A basic 3 zone alarm system. 1 or more sensors are connected in series to each zone | Source

How Burglar Alarm Sensors Work?


Sensors are electronic/electrical devices and in the context of security alarms, they either detect entry of an intruder into a building via a window or door, or directly detect the intruders presence. They are small modules which contain microswitches which are normally closed. The switch contacts are normally "volt free". This means that they are isolated from the electronics of the sensor, so that they can be connected to any external voltage source. When a sensor is activated, the microswitch opens and breaks a circuit. The alarm panel detects this and activates an external wall and internal sounder. The panel may autodial a phone number or send an SMS text message to a cell (mobile) phone. Some alarm systems are monitored by an alarm company to which a subscription is paid.

Typical sensors are:

  • Contacts on windows and doors These contain a tiny reed switch enclosed in a small glass tube within the body of the sensor. The switch is kept closed by a nearby magnet.
  • Shock sensors Used for detecting someone attempting to break glass or otherwise using impact force to attempt to gain entry. These may also incorporate magnetic contacts.
  • PIR Sensors These detect the body heat from an intruder as they walk past the sensor.
  • Microwave Sensors Like PIR sensors, they detect intruders but have certain advantages over them.
  • Pressure Mats Detect intruders stepping on a floor.

What are the Components of an Alarm System?

Alarm Panel

The alarm panel itself may have a rudimentary display consisting simply of LEDs, or a more fancy LCD display may be provided which gives textual information about the status of the alarm, which zone an alarm occurred in, error codes etc.
An alarm panel will also have a keypad for entering passwords and commands.
On some systems, wires from sensors are directly connected to the alarm panel. On other systems, the display and keypad module is kept separate from the incoming wiring from the sensors. The advantage of this is that the alarm panel can be smaller and less obtrusive, while the larger junction box with incoming cable, terminals, battery back up etc can be hidden out of view and away from tech savvy burglars who could hack into the system. Several remote auxiliary keypads without displays may also be provided for arming/disarming the alarm in the vicinity of additional exterior doorways. An attempt at entering an alarm code at the panel (if the sensors have been bypassed) will also trigger a "countdown" of the alarm.


An alarm panel usually has several zones to which sensors are connected. The idea of separate zones is so that when arming the alarm, sections of the installation can be included/excluded from being armed. So for instance, exterior doors could be on zone 1, downstairs windows could be on zone 2, upstairs windows on zone 3, and PIR sensors on zone 4 in a basic setup. When an alarm is armed at night, zone 4 PIRs could be excluded to allow wandering around, and upstairs windows left open by disabling zone 3. When an alarm occurs or cannot be armed (for example due to a window left open), the panel indicates the problem zone.
An entry/exit zone is reserved for genuine entry to the building via a doorway. This zone has a delay associated with it before the sounder operates, allowing a password to be entered to disarm the panel.
More sophisticated entry alarms for larger buildings will have a greater number of zones and the ability to identify activation of individual sensors, possibly indicating the sensor location on a computer screen mimic, depicting the floor plan of the building.
On a wired system, one or more sensors can be connected in series to each zone, known as "daisy-chaining". The disadvantage of daisy-chaining is that if one sensor develops a fault and contacts stay stuck open, the zone has to be omitted during arming, making the other sensors useless until the fault is rectified.
A tamper circuit detects an intruder interfering with alarm system wiring even when it is not armed. This is sometimes called a 24 hour circuit.
A panic button circuit and panic buttons may be included. When a panic button is pressed, the external sounder activates. Panic buttons can be located near doorways, in bedrooms etc.

Backup Power

An alarm panel is usually provided with backup power by a 12 volt lead acid battery. In less expensive systems, nickel metal hydride (NiMh) AA cells may be used. The backup battery maintains power to the alarm panel, sensors and sounder in the event of a power cut or when an intruder cuts the mains power to the panel.


An external sounder operates when the alarm is triggered. Older systems used electromechanical bells. Most modern systems use electronic piezoelectric transducers in the sounder. For added security, a sounder may have a backup battery. This allows it to operate even if the cable connecting it to the alarm panel is cut or power to the alarm panel is removed.

What is a Tamper on an Alarm System?

A basic alarm system uses 6 core cable for connection to sensors, 1 pair for power, 1 pair for tamper and 1 pair for the microswitches in sensors which open when the sensor is triggered. Sensors are typically powered by 12 volts DC. If several sensors are used per loop, the microswitches can be wired in series. One core of the cable travels outwards from the alarm panel to all the sensors, and another core of the cable returns to the panel to complete the circuit, similarly for the tamper circuit.

A tamper or 24 hr circuit consists of a pair of tamper cores in the alarm cable and momentary tamper switches in sensors, the alarm panel, junction boxes and sounders. These switches are maintained in a closed position by lids/covers on sensors and other components of the system. If anyone removes a lid while the alarm is unarmed, or cuts a cable, (cutting through the pair of tamper wires) a warning sounder will indicate this situation (but the exterior sounder may not activate). If the alarm is armed, the main sounder will activate.
Some sensors, e.g. door and window contacts don't have any integrated electronics or tamper switches and so only 2 cores of the alarm cable are required.

If all this sounds like gobbledygook have a look at the diagrams below and it should be clearer!

Wiring of Loop to Panel

Wiring of alarm contacts in sensors to the control panel (power and tamper not shown). In this example, the contacts are "daisy chained" or linked together in series.
Wiring of alarm contacts in sensors to the control panel (power and tamper not shown). In this example, the contacts are "daisy chained" or linked together in series. | Source

Inside a Sensor

This PIR sensor has 3 pairs of terminals. Alarm contacts are normally closed (n/c) and open on activation .Tamper contacts are n/c and open when lid is removed.
This PIR sensor has 3 pairs of terminals. Alarm contacts are normally closed (n/c) and open on activation .Tamper contacts are n/c and open when lid is removed. | Source

Wiring Two Sensors in Series

Sensors can be wired in series on a zone. A core of the cable for both tamper and alarm contacts loops back from the last sensor in the zone to the alarm panel. An EOL resistor may be included in series at the last sensor.
Sensors can be wired in series on a zone. A core of the cable for both tamper and alarm contacts loops back from the last sensor in the zone to the alarm panel. An EOL resistor may be included in series at the last sensor. | Source

Wiring 2 Door/Window Contacts in Series

Door/window contacts can be connected in series. They don't require power and usually don't have tamper microswitches. An EOL resistor may be included in series at the last sensor.
Door/window contacts can be connected in series. They don't require power and usually don't have tamper microswitches. An EOL resistor may be included in series at the last sensor. | Source

(EOL) End of Line Resistors

Older alarm systems as described above had zone loops which were either closed circuit when no sensors were triggered or went open circuit when a sensor activated. This resulted in a low voltage or high voltage respectively at the control panel. The flaw in this system was that a burglar could short out zone wiring between panel and sensors, effectively bypassing them. Then at a later stage they could attempt a break in. Because the zone was shorted, when a door/window contact opened or a sensor activated, it would be undetected by the control panel. Newer alarm systems are made more secure by adding a resistor, typically about 5k, at the end of the loop. This is known as an end of line (EOL) resistor and adds supervision to the loop by detecting shorted wiring. The panel now has 3 voltages it can possibly measure, high voltage with the loop open (due to a broken/cut wire, or a sensor activating), low voltage if the zone wiring is shorted by a fault/burglar, or an intermediate voltage in a non fault/non triggered scenario.
EOL resistors must be fitted at the last sensor in a loop so that the panel can detect when a burglar shorts the two alarm cores in a cable "upstream", that is on the panel side of wiring to sensors. If resistors are fitted in series with the loop at the panel, they cannot detect that this has occurred.

Fully Supervised Loop (FSL) and Closed Circuit Loop (CSL) Wiring

Basic alarm systems use 2 cores for sensors, 2 cores for tamper and 2 cores if needed for powering sensors. The problem is that a global tamper is used and this loops through all the zones on the panel. So if a burglar cuts a cable, this deactivates the tamper for all zones and potentially puts the system out of action until the break can be pinpointed.
Fully Supervised Loop wiring provides a separate tamper for each zone, so if a cable is cut or a loose connection occurs in the tamper circuit, only that zone will be out of action and also it's easier to trace the fault. An EOL resistor is used at the last detector plus in addition a resistor across the contacts of each sensor in the loop. The system can then differentiate between a no alarm condition, a tamper, or an alarm condition, using just 2 cores of cable for both contacts and tamper.

Door / Window Contacts

These come as two parts, the contact part and a magnet. The contact part consists of a small plastic module containing a reed switch (a miniature switch enclosed in a thin glass tube) which is mounted on the door jamb or window frame. The magnet part is fixed to the door, or window sash / casement so that it is close to the contact part when the door or window is closed. This keeps the reed switch in a closed state. When a window is opened, the magnet moves away from the contact and the reed switch opens.
Contacts don't require power and only 2 cores of a cable are required, however if 6 core cable is used, 2 unused cores in the cable can be used for powering sensors added to the system at a later stage. Usually they don't have tamper contacts either, however 2 of the cores can be wired to tamper contacts in junction boxes or sensors, during modifications/upgrade to the system.
Shock sensors and magnetic contacts are also available as a combined unit.

Window contact and magnet
Window contact and magnet | Source

PIR Sensors

These sensors use an element sensitive to human body heat. When someone walks in front of the sensor, electronics in the device opens a microswitch which triggers an alarm.
PIR sensors have varying ranges and detection profiles over which they are sensitive. Usually they have near, far, and possibly intermediate zones through which an intruder must pass before triggering an alarm. Normally sensors are sensitive over at least a 90 degree sector, but omnidirectional versions are available.

Shock Sensors

Shock sensors are bonded to glass in a door or window or fixed to the frame. During setup, the sensitivity of the sensor can be set and the number of impacts which trigger an alarm. Some sensors are "intelligent" and can detect the sound of breaking glass.
Shock and magnetic contact sensors can be combined into one unit.

Troubleshooting Sensors Which Don't Work or Cause False Alarms

There are several causes of false alarms or sensors which fail to operate:

  • Issues with PIR sensors
  • False triggering of shock sensors
  • Loose connections
  • Alarm contacts in sensors becoming faulty
  • Tamper switches becoming faulty
  • Voltage spikes on supply
  • Backup battery problems
  • Badly placed or damaged wiring

Remember you can use a shorting link at the terminals of the panel if you need to isolate any zones for testing purposes (e.g to test continuity of a loop) or to disable a zone. A short piece of insulated wire is ok. This allows the alarm to be used normally while testing.

Checking the Loop Resistance

Alarms are triggered when a normally closed (NC) microswitch in a sensor, or a tamper contact goes open circuit. The resistance of a loop circuit (consisting of sensor contacts and loop wiring all connected in series) must be below an upper limit with all switches closed. This is usually 5 to 10 kilo ohms, but depends on the panel. Also the resistance of the loop when a contact opens has a lower limit, in the range of 100 kilo ohms. To check the resistance of a loop, remove the two wires connected to the zone input at the alarm panel and connect the probes of a digital multimeter, set to the ohms range, to these two wires. Resistance should typically be less than 100 ohms (or around 5k if an EOL resistor is fitted at the last sensor), but can rise if sensors are giving trouble or if you have many sensors connected in series and long cable runs. If the resistance is excessively high, several hundred ohms or greater, further investigation is necessary. If you have an assistant, they can watch the meter and you can bridge the alarm contacts of each sensor in turn with a piece of wire. By a process of elimination, this will enable you to identify the problematic sensor. Alternatively, you can go to each sensor in turn with the meter and measure the resistance across the alarm contacts. Remember that the loop must be disconnected from the panel, otherwise voltage will be present on the contacts, giving a false reading. Also PIRs and other sensors requiring power must be powered up for the contacts to operate.

See this guide for instructions on how to use a multimeter:

How to use a digital multimeter (DMM)

Issues With PIR Sensors

PIR sensors are triggered by movement of humans walking perpendicular to the sensor through its sensitive zones. If a sensor is mounted outdoors, it can also be triggered by cats or other large animals. Sensors are available which are only sensitive to human movement. If a sensor is located in a shed/garage, it can be triggered by bats, birds or rodents which have made their way into the building.
Another cause of nuisance triggering is a badly placed PIR which points at a stove or radiator and picks up movement of warm air. It is also not recommended facing a sensor towards a window to avoid picking up variations in heat caused by the sun. Sensors can't "see" through glass and have dual element sensors to make them insensitive to overall changes in sunshine level. I'm speculating here, but large changes in IR intensity caused by cloud movement could trigger a sensor if it faces out a window.
Sensors should be placed so that intruders are likely to walk perpendicular to the device, through the sensitive zones. Also the sensor should be mounted in a suitable position in a room, at an appropriate height on a wall and angled in such a way that intruders cannot crouch down and pass through a blind zone (i.e low and close to the sensor). See diagram below. Instructions provided with sensors normally provide diagrams outlining the regions of sensitivity.

Zones of Sensitivity for a PIR Sensor

A PIR is most sensitive to intruders walking perpendicular to the zones
A PIR is most sensitive to intruders walking perpendicular to the zones | Source

Loose Connection Repair

Loose connections are always a cause of problems with any electrical or electronic device. When installing sensors, screws should be screwed down tightly on the cores of alarm cable, and ideally boot lace ferrules should be used to keep the strands of wires together. Ferrules are crimped onto the ends of wire and prevent the fine strands of wire of from being damaged by screws of terminals. They also make it easier to remove and replace wires from terminals, and have a shroud to prevent inadvertent contact between loose strands of wire and adjacent terminals.
Connections can also become corroded over time, especially in damp environments.

Boot lace ferrule
Boot lace ferrule | Source

False Triggering of Shock Sensors

This type of sensor can be subject to false alarms caused by hailstones hitting windows, or more likely skylights, birds seeing their reflections and banging on glass or even impact of heavy traffic on roads close to exterior walls. There may be a setting inside the sensor to reduce the sensitivity. Also the number of impacts required to trigger an alarm can usually be set and this may need to be increased.

Alarm Contacts in Sensors Becoming Faulty

Over time, the resistance of microswitches in sensors can increase. Ideally the resistance of a closed switch should be zero ohms, but this can become higher as switches age. If doors and windows are rarely opened, the reed switches in magnetic contact sensors can become "sticky" and fail to open, preventing the alarm from activating if an intruder breaks in. Another possibility is that the magnet can become weak, failing to keep the contact closed, especially if it wasn't placed close enough during installation. This can cause nuisance triggering, when e.g. vibration from wind or heavy nearby traffic is sufficient to shake the contact open.
To check the resistance, set your DMM to the ohms range and measure resistance between the screw terminals. The loop should be disconnected at the alarm panel to remove voltage from the terminals, and of course in the case of magnetic contacts, the magnet on the window or door should be adjacent to the contacts to keep the reed switch closed.

Testing Magnetic Contacts

Set the DMM to the ohms range and measure resistance between screw terminals of contacts. The loop should be disconnected at the alarm panel to remove voltage from the contacts.
Set the DMM to the ohms range and measure resistance between screw terminals of contacts. The loop should be disconnected at the alarm panel to remove voltage from the contacts. | Source

Tamper Switches Becoming Faulty

Tamper switches consisting of a spring operating a microswitch are used to detect someone removing the lid of a sensor or other components of an alarm system. An alternate style of switch consists of springy, nickel coated metal strips, pushed together when a lid is in place. These strips can tarnish over time, contributing to an increase in the loop resistance. This can produce false alarms as contacts expand and contract, and move relative to each other during hot or cold weather. Contacts can be cleaned with a piece of fine wire / steel wool and then wiped with rubbing alcohol / IPA (Isopropyl Alcohol). Don't overdo it because the coating (It's either nickel or chrome) could be removed.
Sometimes sensors have tamper microswitches that are closed by a projection on the lid (often a small round piece of rubber) of the sensor when it is replaced. It can happen with badly made sensors that the rubber piece on the lid gets squashed over time and loses its springiness, so it doesn't put enough pressure on the microswitch. The symptoms are a sensor that generates a tamper when knocked (and possibly may do so if there is nearby heavy traffic causing vibration).
Alarm panel lids can also cause tamper faults, so check they are seated properly when replacing.

Tamper Contacts in a Junction Box

Tamper contacts in a junction box (the outer casing has been removed)
Tamper contacts in a junction box (the outer casing has been removed) | Source
Clean with fine wire wool and IPA
Clean with fine wire wool and IPA | Source

Voltage Spikes on Supply

Voltage spikes on your mains supply are caused by disturbances such as heavy loads being switched on and off in the locality, generators coming on and going off line, switching activity in substations and lightning strikes. These spikes can trigger false alarms. Your alarm is likely to be powered directly via a cable from the electrical panel in your home or via a spur from a cable via a fused connection unit. A surge filter may give some protection from false alarms caused by spikes injected into the power supply of the alarm panel.

Backup Battery Problems

A lead acid or NiMh battery is used to keep an alarm alive in the event of power failure due to an interruption of your supply or deliberate cutting of power by an intruder. These batteries have a limited lifespan of 3 to 5 years. As a battery ages, its voltage can fluctuate, injecting noise spikes into the system.
When a battery nears the end of its life, its capacity decreases and the length of time it can maintain backup decreases.

Badly Placed or Installed Wiring

If wiring is run adjacent to power cables, voltage spikes can be coupled directly into the alarm cables. During installation, staples or clips may have cut through alarm cable. This can cause problems later as cores get shorted out. Also if you have had workers in your home doing renovations, make sure they haven't dislodged or damaged sensors, cables etc.

Buttons Not Working on the Keypad

Although older alarm panels may have keys which are actually push buttons (like what used to be used on computer keyboards), newer keypads are usually membrane type. These have "contacts" printed as pads onto a PCB, and conductive rubber pads on a moulded flexible membrane. When a key is pressed, the rubber pads press against the PCB and complete a circuit. This type of keypad is also used on TV remote controls. Over time, the conductive rubber pads lose their conductivity, however they can be repaired. See this article: How to Repair a Keypad or Remote Control With Kitchen Foil

The keypad of an alarm is similar to this membrane keypad from a remote control
The keypad of an alarm is similar to this membrane keypad from a remote control | Source
The conductive pads on the membrane make contact with copper contact pads on the PCB
The conductive pads on the membrane make contact with copper contact pads on the PCB | Source

Did You Fix Your Alarm Using the Info in This Article?

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Questions & Answers

© 2014 Eugene Brennan


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    • eugbug profile image

      Eugene Brennan 2 weeks ago from Ireland

      It could be, but check that any fuses are ok. These are often 20mm, 1A glass types. Replace fuses only with the same type.

    • profile image

      Walshe2 2 weeks ago

      Hi,I have a hkc outside bell box that is not going off in an alarm situation so I replaced it with a new one and have the same problem.I have checked all cables but found that back at the control panel there is no voltage at the external bell terminals.could the PCB be faulty???

    • eugbug profile image

      Eugene Brennan 4 weeks ago from Ireland

      Hi Damion,

      Voltage is usually 12 volts to sensors/contacts, so not a hazard, but to be doubly sure there isn't a mains electrical wire putting dangerous voltages on the wiring, you can always check with a neon phase tester screwdriver.

      The issue could be due to a loose wire. It can also be caused by a faulty contact, but sometimes the magnet can lose strength and not keep the contact closed anymore, especially if the magnet wasn't mounted close enough to the contact in the first place. Contact/magnet spacing should be 1 cm at the most. You could try moving the magnet closer (maybe put some sort of spacer underneath) and see if it improves matters.

    • profile image

      Damion 4 weeks ago

      Hi, There appears to be an issue with the front door magnetic sensor. The door is closed but we are hearing a "beep" as though the door has opened. This then sets off the house alarm. I tried to move the wire by the sensor the beep occurs. Could this just be a loose wire? is there much voltage within the sensors so that I know its safe to check myself?

    • eugbug profile image

      Eugene Brennan 5 weeks ago from Ireland

      Haven't been able to find any info on the Abacus panel, but try and they might be able to help.

    • eugbug profile image

      Eugene Brennan 6 weeks ago from Ireland

      Hi Chris,

      I'll see if I can find any reference to the error and get back to you tomorrow.

    • profile image

      Chris J 6 weeks ago

      Hi Eugene

      I have an Abacus LCD alarm panel and all of a sudden its started playing up a little. Its fine until the alarm is set and then as soon as its armed it will sound after around a minute every time, the log shows the reason for the alarm to trigger as "KP1 Engnr". Any clues what could be causing it?

      I've already tested the battery in the main box and the voltage is constant and fine.

      Any helps appreciated, very nice of you to help all these people through your site.


    • eugbug profile image

      Eugene Brennan 6 weeks ago from Ireland

      Hi Rami,

      The Veritas R8 is not wireless unless a module has been added to make it so. A sensor that acts up could be faulty, require a battery if it's wireless, or the wiring has developed a fault somewhere along the line, perhaps due to renovations. Motion sensors can also be triggered by sudden changes in temperature e.g. if they face a window or radiator.

    • profile image

      Rami T 6 weeks ago

      Hi Eugene

      I have Veritas R8 from Texecom . I think it is wireless. one of the motion detectors kept alarming unnecessarily on/off!

      What do you think the problem is?

      Thanks for answering

    • eugbug profile image

      Eugene Brennan 7 weeks ago from Ireland

      Is this a wireless system? The battery may need replacement in the keypad.

      If the system is wired, and this is a remote auxiliary keypad, again there could be a flat battery in the pad.

      If the keypad is wired and separate to the main alarm panel, connection box, trace the wiring and see if the panel/box is feeding the keypad with 12 volts. There may be a fuse blown in the panel, so check that first.

    • profile image

      david 7 weeks ago

      my key pad has no power to it yet my sensors are lighting up red help

    • eugbug profile image

      Eugene Brennan 8 weeks ago from Ireland

      Hi Lindsay,

      Normally external sirens won't activate unless the system is armed and you start opening sensors, the panel, junction boxes etc. However if you do the same when the system is unarmed, a sounder will normally activate on the panel to indicate that tamper loops have gone open circuit. Whenever I'm working on my panel and this happens, I just enter the code to silence the sounder. The external siren will operate if the wiring for a panic switch goes o/c, or the cover is opened, irrespective of whether the system is armed or not, so you may want to have a wire link ready to short out the contacts until you're ready to replace the cover on the switch if it's a wired type. I'm not sure about engineer mode on your panel. Usually there's a time period during which work can be done before any sounders operate, but even if that happens, I'm sure you can just exit and re-enter engineer's mode to reset this period.

    • profile image

      Lindsay 8 weeks ago

      Hi, I need to change my magnetic door contactor, a vibration sensor and panic alarm switch. Thanks to internet info, I have managed to sus the engineers code for our Paragon Plus alarm; hence, once the system is in Engineers Mode, can I do the work without triggering the sirens?

    • eugbug profile image

      Eugene Brennan 3 months ago from Ireland

      Hi Jayne, If you knew the model of the alarm, it may be possible to source a manual to see what the flashing LED means.

      You could try posting on this forum. There are lots of members who are installers and would be familiar with specific models of alarms.

    • profile image

      Jayne 3 months ago

      Hi my telstar alarm green light on the control panel and the main box is flashing and id like to fix it how do i go about doing that? The company is out of business so i have no one to ring.

      It dose work but it didnt do this before any idea? Thanks

    • eugbug profile image

      Eugene Brennan 3 months ago from Ireland

      Hi Maria,

      There's probably an issue with the battery being charged. Possibly a blown fuse, or a fault in the charging electronics.

      Check also mains power is going to the alarm. There may be an LED to indicate this on the panel (which may be a separate unit, or integrated with the keypad).

    • profile image

      Maria 3 months ago

      Hello my alarm keeps beeping says low battery we already replaced the battery still the same

    • eugbug profile image

      Eugene Brennan 4 months ago from Ireland

      Hi Fred, You can try the manufacturers here:

      ..but depending on your country, manufacturers may or may not give out technical information for security reasons unless you are a registered installer.

      Have a look at this page which covers changing the PROM:

    • profile image

      Fred 4 months ago

      Hi Eugene, I have a Gemini P1632 and I need to change a component in the motherboard. where do I find technical information about this ?

      Thank you very much.

    • eugbug profile image

      Eugene Brennan 5 months ago from Ireland

      Hi Richard,

      There are several methods. You can try cleaning the conductive rubber pads under the buttons with IPA, but this only seems to work temporarily. Another option is to buy replacement rubber pads and stick them on to the existing ones. Yet another solution is to cut out foil disks with a paper punch (as used for making holes in paper when putting it into a ring binder) and then stick this onto the pads. I did this with a keypad a few years ago and it's still working.

      I've written a guide about it here:

    • profile image

      richard 5 months ago

      i have a much used keypad and the top three numbers that were our code no longer make contact easily so we changed our code. is there a way of mending them without buying a new keypad?

    • eugbug profile image

      Eugene Brennan 5 months ago from Ireland

      Hi Nikki,

      Is this a PIR sensor and is the alarm wired?

      If it's a wired alarm, I assume you've checked connections at the sensor to ensure they are tight, and similarly at the panel. Check also connections at any intermediate sensors in series on the loop. If there are any junction boxes in the zone, check these also.

      Has any home improvement work been carried out which may have damaged the cable, or could it have become fatigued over the years from flexing?

      Has electrical mains wiring been installed close to this zone's wiring?

      Could cable have been damaged by rodents?

      Do false alarms occur during the day or night and at any specific time and is there any pattern to the event?

      It could be an issue with the panel's PCB. Maybe a dry solder joint is acting up after after the connection has oxidised over the years. To eliminate a wiring continuity problem or something else triggering the sensor, I would bypass the zone by removing the contact cores from the screw terminals and add a shorting out link and see if this prevents false alarms. I'm not sure whether this is possible, but maybe electromagnetic interference from nearby high power radio transmissions could be inducing voltage in the cable. I know from experience that if mains cable runs close to alarm cable, unplugging appliances can trigger an alarm.

    • profile image

      Nikki 5 months ago

      Help, one zone all of a sudden kept going off after 9 years of nothing, I've replaced the sensor in that zone, the main alarm has had a new battery and new fuse yet that same zone is still going off every now and then, no spiders, now webs, no animals, no draft, please help it's starting to drive me and the neighbours mad. Thanks

    • eugbug profile image

      Eugene Brennan 7 months ago from Ireland

      Hi Mark,

      The alarm shouldn't be set off when not armed and the contact on a zone opens. The only thing I can think of is that either the contact is wired incorrectly into the tamper circuit (in which case the tamper sounder would activate at the panel, but not the external sounder) or alternatively it's wired into the panic circuit, in which case it would set off the alarm and activate the external sounder (if there is one and the alarm isn't some form of monitored, silent type).

    • profile image

      mark 7 months ago

      I have door contact which sets the alarm off when you open door when the alarm is off. i hace replaced door contact and when you tryand set alarm the panal its saying open zone.


    • profile image

      Mark R 7 months ago

      Thanks for your help, the problem was a wire that had come away. Replaced both batteries & now have a fully functional alarm again. Happy days

    • eugbug profile image

      Eugene Brennan 7 months ago from Ireland

      Hi Mark,

      I don't think the external battery if it's in a sounder, should cause a tamper indication.

      Maybe you have to clear or acknowledge the tamper before the tamper light goes out?

      Check all lids on junction boxes, sensors and panic buttons. Also check the tamper spring on the panel hasn't become dislodged/fallen out.

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      Mark R 7 months ago

      Wonder if you can help. I've a veritas 8 alarm with a solid red tamper light. The tamper loop is already bridged on the circuit board & no zones appear if I do a prog19 test for faults. The internal battery was dead but has been replaced.

      Can the external battery that I'm assuming is dead too cause a solid red tamper?

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      Chris 8 months ago

      Thank you for your help. It was a failing sensor / weak magnet. I replaced the sensor and magnet and it works perfectly now.

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      Eugene Brennan 8 months ago from Ireland

      Hi Paul,

      Bats, birds and possibly spiders can trigger PIR sensors, but if there's an LED on the box for each zone which indicates that an alarm occurred in the zone, it should light up. Try causing an alarm on the other zones and see if if the box indicates this. Then maybe it's a case that the indicator is at fault. However there is the secondary problem of what is triggering the alarm. Are there just LED indicators on the panel or an LCD display which gives more info? Does the alarm just consist of magnetic contacts on entry/exit doors and PIRs? Lots of things can trigger false alarms including loose connections in wiring, tamper contacts getting tarnished in junction boxes and moving when they expand and contract due to temperature changes (the sort of thing that can cause connection problems in a torch), over sensitive vibrations sensors triggered by hail stones on windows or heavy traffic, voltage spikes on lines etc.

      Possibly the software on the alarm has gone wonky requiring a reboot, but this is likely a job for the service technician. Is there a 'warranty' period for the service?

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      Paul Topper 8 months ago

      I'm having a annoying problem where the alarm goes off 15 minutes or so after it's set, but no red lights show on the box to suggest what is setting it off? The alarm is about 10 years and was fully serviced, with the back battery replaced last summer.

      Any ideas why it's suddenly giving false alarms, could a spider etc trigger the PIR's but not the red lights?

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      Eugene Brennan 8 months ago from Ireland

      Hi Chris,

      Sounds like a loose connection or possibly the magnet has weakened so it's ability to keep the reed switch contact closed is borderline. Sometimes contacts can stick closed, but it's possible that they can transiently open due to vibration if the magnet is barely keeping them closed. It's probably best to replace the contact, but before you do that, if possible, join the two contact wires together and leave for a period to see whether the zone is going o/c somewhere along the wiring.

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      Chris 8 months ago

      Great post however I am having a slight issue with my magnet door contacts that I couldn't find an answer too.

      When I open the door the zone shows open, when I close the door the zone shows closed. However about 2 seconds after I close the door the zone goes into open mode again and takes a couple minutes to go into close again. This is the only sensor on the zone.

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      Eugene Brennan 9 months ago from Ireland

      From a reader's email query:

      "My alarm has the tamper light on and wont work at all. Initially the alarm went off and my neighbour went in, and took one of the senser covers off. This didn't stop the ringing but the ringing stoped when she put the code in. We have put the cover back on but the alarm's not working. Also the alarm control box feels a bit warm on the top. Do I need an engineer? Thanks for any assistance you can give."

      A tamper indication means that the lid of a junction box, sensor, sounder/bell box cover, panic button button lid etc is loose. It could also be because of a loose wiring connection. Depending on the alarm, if the tamper activates, the strobe light (if there is a strobe light) on the sounder on the wall outside may activate. This requires extra power from the alarm panel which could explain the heating.

      It's probably best to call an engineer who would be experienced with this stuff and resolve the problem quickly.

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      Eugene Brennan 11 months ago from Ireland

      Hi John,

      I presume by "pair" you mean PIR?

      Sensors don't necessarily have to giv an indication on movement, but usually they are set to do so. If the system is wired, it could be a problem with the voltage supply to the sensors. You would need to check this with a DMM (multimeter) at the sensors. It should be 12 volts. If it isn't, trace the wiring and check it's ok at the panel.

      I don't know why the indicator on one of the sensors goes from dull to bright. This could be normal, but also the sensor may be faulty. Is this sensor able to trigger an alarm?

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      John Osborn 11 months ago

      I have 4 pair sensors on my system, one is lit all the time and goes from dull to bright and the other 3 are not lighting on movement at all any ideas why this is happening.



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      Eugene Brennan 12 months ago from Ireland

      Hi Michael.

      It sounds as though the sensors are dodgy. Usually sensors get stuck closed and the reed switch contacts don't open when a window/door is opened, but they can go faulty the other way and not close. If you don't have too many contact sensors, you could try bridging the contacts with a wire link, then wait and see if the problem is resolved. If it isn't, possibly there is an intermittent bad connection in the wiring/junction boxes and the loop goes open circuit when temperature rises falls.

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      Michael Ringer 12 months ago

      I have one zone on my windows that says its always open even though it isn't. Some times i can put magnets on the sensors and it fixes the situation for 24 hours then the zone says its open again. What is the solution for that?


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      Eugene Brennan 15 months ago from Ireland

      Hi John,

      Bells/sounders often have an internal rechargeable battery to cater for the situation you describe, i.e. power is cutoff (by a burglar), or the cable to the bell is cut. Usually the backup battery in the alarm panel (or separate box if you have a remote keypad) keeps the panel alive plus provides a voltage signal to the bell if mains power is removed. However if the panel has no battery or the battery is defective, this voltage will drop to zero when mains is removed and this is likely what is triggering the alarm.

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      John Woodgate 15 months ago

      My outside bell goes off when I turn off the mains power can you advise please thanks

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      Eugene Brennan 15 months ago from Ireland

      If a panel has LED indicators, these are usually power, tamper (24 hour), panic (PA), and then an indicator for each zone, which light up if the zone isn't clear. Do you think it's one of these indicators which is lighting up for the kitchen zone? Is this the sensor you removed for painting? It's difficult to check anything without a meter. If you had one you could check continuity of the tamper loop by removing the pair of tamper wires at the panel, connecting the meter probes to the wires, then wiggling the wiring at the sensor you removed for painting to see if there's an intermittent break in the wiring.

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      andrewro55 15 months ago

      HI Eugene, thanks for the tips, since i posted the first comment (I posted the first comment but didn't show in my feed as I had not logged in) then i have been fiddling with it, hence the second post. Got all the pir's lighting up now, alarm pad is off tamper, i put a wire in the box looping both tamper connections (from another post). When i set the alarm now it shows a red light on the kitchen zone (fault?) I will check the wires again and if still showing a fault maybe buy a new pir as I dropped it yesterday too?? i don't have a voltage meter, thanks for your help.

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      Eugene Brennan 15 months ago from Ireland

      Hi Andrew,

      Check the reply I posted yesterday. If you disconnected any of the wires from the sensor you removed to do your painting, check they were put back into the correct locations in the terminal block of the PIR (have a look at the other PIRs or the control panel to see what colours are used for tamper, power and contacts). Also the tamper core in the cable feeding the sensor could a broken conductor.

      Are your other sensors showing an indication of movement now? In your original post, you said they weren't?

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      andrewro55 15 months ago

      HI Eugene, i took off a pir in the kitchen to paint and when i put back the alarm it says tamper. I have had a few of the other pir's off to check wiring but seem ok. I had a 1 amp fuse blow in the box but renewed this too. The alarm say tamper and all my pir are light up with movement. any ideas, much appreciated. its an accenta. cheers for the help.

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      Eugene Brennan 15 months ago from Ireland

      Hi Andrew.

      Check the wiring of the original PIR you removed to ensure there are no loose or broken wires in the tamper circuit. It sounds as if you've lost the 12 volt power to the sensors. Make sure there are no other fuses blown at the panel and use a multimeter to ensure that 12 volt is actually present on the terminals feeding the wiring for the PIRs. Then check whether 12 volt is present at the sensors. Also the original sensor could have blown the fuse again if there's any wires/strands of wires touching at its terminal block. Hopefully the 12 volt supply regulator hasn't blown on your panel, but if you can't measure a voltage, remove the positive power wire of the cable feeding the sensors (at the panel) and see if 12 volt is then present. If it is, a sensor/wiring may be pulling the power line low.

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      Eugene Brennan 15 months ago from Ireland

      Hi Jane.

      The panel may have been reset to the default password which for a 4 digit password could be 0000, 1234 or similar.

      Does the panel say incorrect password or just not acecept input?

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      Jane 15 months ago

      This is a great artical !! Yet it doesn't solve my problem with my alarm system my alarm is in working order but just won't accept my passcode recently I had an electrician fit 2 new smoke alarms and since then my alarm has failed to activate would you know how to help me please eugine )

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      Eugene Brennan 17 months ago from Ireland

      Hi Gilly, sounds as if the settings in memory may have been lost during the power fault. You could try setting a new password and see if that works. This seems to be the user manual:

      Which model Abacus keypad do you have?

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      Gilly 17 months ago

      We had a fuse trip the electricity panel. When the panel came back on the alarm showed power fault and was cleared but now the when I put my number in it goes to 'setting ok' but does not set - it's as though it's stuck. When I put the number back in it goes back to off. It is an abacus key pad if that helps. Can you help? Thank you

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      Eugene Brennan 18 months ago from Ireland

      Before you try using glue, check whether it's possible to move the magnet upwards (assuming it's at the top edge of the door), and re-drive the screws adjacent to the existing holes.

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      Eugene Brennan 18 months ago from Ireland

      Hi George,

      The cover is probably like a box which you should be able to prise off from underneath with a screwdriver (prise up one side a little then the other side until you get it off).

      If you're lucky, the fixing holes in the magnet will be slots, allowing some adjustment. However if they aren't, you'll either have to relocate the two halves of the sensor, or you could try removing the screws and gluing the magnet to the door with a "no more nails" type adhesive product. (there is a double sided tape version of this also).

      (These might be a little thick though and a thin layer of glue would be better)

      If the door hasn't dropped much, there shouldn't be an issue with the contact not working. The range is usually about 1/2 an inch or so before a contact opens when the two halves are separated. However it can be borderline and you may be getting spurious false alarms. Over time also, contacts can get "sticky" and fail to open, especially if they are fixed to windows which are never opened (so the contacts don't get "exercised"). So if you have any more, it's worth checking them out. When installing an alarm system, it's wise to have e.g. PIR sensors included as "belt and braces" should this happen.

      Hope this helps George!

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      George 18 months ago

      My front door has dropped slightly creating a gap between the two halves of the contact. Can I remove the bottom contact from the door and move it up a little? How is it attached to the door? I assume there's a cover that slides off revealing screws through the back part of the plastic.

      Thank you kindly!

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      Eugene Brennan 20 months ago from Ireland

      If the cables are still attached to the alarm panel, one the cores may carry 12 volts (although only 2 cores without a voltage supply is necessary for contacts so there may be no 12 volts present). If you cut through the cable, it may possibly short out the 12 volts momentarily and blow a fuse at the alarm panel. If you can trace the wiring back, the best thing to do is de-energise the panel by powering down the mains supply to it (remove the fuse in a fused connection unit or turn off the MCB for the panel). Disconnect the backup battery, and then disconnect the 12 volt core in the alarm cable/cables which travel out to the windows. Are you going to fit the contacts to the new windows?

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      Doug 20 months ago

      Some of our window contacts have been remover by window fitters leaving lengths of cable which they've tied up. Is it safe to just cut these off?

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      Eugene Brennan 21 months ago from Ireland

      You could try replacing the transformer (which would have to have the same VA rating, input and output voltages as the original), but there's no guarantee the board isn't "fried", or damaged and potentially a fire risk.

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      Eugene Brennan 21 months ago from Ireland

      Hi Bret. If you measure resistance with the transformer still connected, you will get very low resistance (because the transformer secondary has such a low resistance), so you would need to disconnect the input wire to the board to measure the resistance. If the transformer got an overvoltage from the line failure, the chances are that a fuse built into the windings of the transformer may have blown, and these are not replaceable. Check also for blown fuses on the circuit board of the alarm.

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      Bret Schaller 21 months ago

      We lost a transformer and a single leg of the 3 phase power coming into our building. I also had a PC power supply fail along with the alarm system going blank. The AC/AC transformer power the alarm no longer works. Where this power supply attaches to the alarm board - there is zero resistance across the two contacts. I'm sure connecting a replacement power supply will short the power supply. What's your advice? Is it time to upgrade my alarm system?

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      Faith Reaper 23 months ago from southern USA

      Oh, thank you, Eugene.

      That makes a lot of sense about the loose connection in a sensor and/or it being a contact/shock sensor on the door because it did receive contact or a bit of a shock so-to-speak.

      You are certainly knowledgeable in many areas it seems from glancing over the topics of the hubs you write about here.

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      Eugene Brennan 23 months ago from Ireland

      Thanks Faith Reaper! Transient problems with an alarm going off can be really annoying because they are so difficult to troubleshoot. Its much easier to sort out a problem where part of the alarm doesn't work at all. Sometimes a loose connection in a sensor can cause the alarm to be triggered by a shock (banging the door as you suggested) or a change in temperature (causing metal to expand/contract with resultant movement of metal surfaces over each other). The sensor fitted to your back door could be a combined contact/shock sensor which would trigger if the door is opened, but also if the door is banged.

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      Faith Reaper 23 months ago from southern USA

      Hi Eugene,

      This is certainly a detailed article here on burglar alarms. I think you've covered all the bases.

      It seems my house alarm will just go off while we are still in the house for some odd reason every now and then. As far as I know, no one was attempting to break in. It actually usually happens during the day on the weekends. To my knowledge, it has never gone off while we were away.

      The other weekend when I had the small children up at the house, I think one of them may have attempted to go out the backdoor but it was still dead bolted and possible hit the door hard. The alarm did go off. Can something like that make the alarm go off?

      Will share on Pinterest and Twitter.