How to Use a Continuity Tester
Before removing any device from a circuit and before accessing the internal workings of any device, you MUST make certain that you have removed ALL electrical power from the unit you intend to repair.
Continuity testers are simple devices designed to verify a complete electrical path through an object or circuit. They are especially useful for checking fuses of all types, lightbulbs, and wire paths.
While there are a variety of devices that include the ability to test for continuity, a homeowner can easily get by with the simple single purpose continuity tester. This is usually comprised of:
- Two leads
- A small body where the leads meet
- Some form of indicator
How to Test Fuses
To test a fuse of any type, remove the fuse from the de-energized circuit either by pulling it completely out or, if this is not possible, removing the lead from one side or the other of the fuse. NEVER ATTEMPT TO TEST A FUSE WHILE IT IS STILL FULLY IN THE CIRCUIT. Sometimes, the signal will backtrack through another path and give you a false reading if you leave the fuse within the circuit.
With the fuse separated from its circuit, simply touch the two leads of the tester, one to each side, to the two contacts/metal caps/sides of the fuse. If the fuse is good, the indicator on the tester will indicate this fact. If it is not good, the tester's indicator will remain immobile.
How to Test Lightbulbs
For a standard incandescent lightbulb, simply touch the two leads, one to the tip of the base of the screw portion, and one to the side of the screw portion of the removed lightbulb. If you are dealing with a cylindrical bulb (such as an overhead lamp in a car) then test it as you would a fuse. THIS TYPE OF TESTER WILL NOT WORK WITH FLOURESCENT BULBS.
LEDs require a certain level of voltage, usually just over 1 volt, to force their internal circuit into continuity. Make sure your continuity tester is designed to test LEDs if this is your need.
How to Test Wiring
You may also use this tester to verify that there is no break in a wire run. This ability is limited, of course, by the reach of the tester's leads but can be useful before making the final trims on audio wiring.
Touch one of the leads to the starting point of the unenergized wire and touch the other lead to the ending point of the unenergized wire. If there are no breaks in the wiring, the tester will indicate continuity.
When testing a wire run, it is allowable to temporarily tie in a jumper wire to one end in order to get your wiring to reach the leads of the continuity tester.
Be aware that longer wire runs may fail a continuity test with your small tester simply due to the length of the run and not because of any break in the line. For longer runs, it is recommended you use a more expensive, better-designed tester to overcome this limitation.