I have a Gilbert furnace and the inducer runs. The igniter glows brightly. The gas valve did not turn on to produce a flame when it is cold outside, like zero. Does the flame sensor detect the hot surface igniter is hot? Or does something else turn on the gas valve?


Great breakdown of info! So all I can do is narrow it down but this is how I'd proceed. First suspect, pressure switch. You can test with a voltmeter to make sure it's closing once igniter begins to glow. Or by jumping it out and see if it fires then. If not, check for flue blockage and listen to inducer to see if sounding slow or something in there. If not, could be gas valve. Test that voltage is coming to it. If not, I'd suspect the board. Keep in mind this is just a process, not a diagnosis. A voltmeter and knowledge of what you're doing with it is important. BE SAFE! Don't do anything you're not comfortable with.

Updated on January 8, 2018

Original Article:

Troubleshooting Common Furnace Problems With an HVAC Expert
By Dan Robbins