How do l tell if my ignition module is faulty or is it the spark ignitor?

The furnace is a Carrier Day & Night about 17 years old model number 394JAZ0480800AAFA.

Usually the spark ignitor is not bad unless it has the 3 wire pilot. The 3 wire pilot assemblys do go bad. The module does go bad also from time to time.

Yeah, but how does he troubleshoot it?
Ferenc

With a volt meter and use the wiring diagram.


A new BDP 740 pilot assembly will typically energize the main valve within 45 seconds (I like to see 20 or so) of establishing flame. You need to find the main valve output from the pilot and test for voltage to ensure that the switch is 'throwing'. Consult the wiring diagram (of course I know which wire it is, but you cannot learn unless you try on your own and if I just told you outright it would take all the fun out of it for you.) Study the pilot flame to be certain that the spark extinguishes shortly after lighting. Almost all BDP product kill the spark module when switching over to main valve. CHECK YOUR MANIFOLD PRESSURE--very low pressure will not provide a flame large or hot enough to throw the pilot switch...

OK, so I took mine apart. The igniter is a two terminal device with a short cable and connector. Turn off power to system, disconnect igniter. Measure its resistance. If it's open, it's bad.

Hope that helps - oh, and I'm NOT A REPAIR GUY.

Is this a silicone ignitor?
That model is supposed to use 3 wire safety.
The fun part of this is that you new how to fix it to start with. LOL
But just in case it doesent work.
Jumping white and yellow allows the main burner to come on. If when you remove the jumper from y/g and the pilot goes out that means the "hold" coil has failed and gas valve needs to be replaced. Have you taken a voltage read at the 2 terminals of the spark gen yet, with t'stat calling for heat? Also the high voltage redish wire is not hard wired in. You should be able to just pull it off the spike. Oops you said you tried the screwdriver test & no arc. DO NOT tryand take voltage read at the high voltage spike. This is around 15,000 volts. Just test for voltage coming in & than the screwdriver drawing an arc.