OK - another weird problem.
Make/Model: Payne Heating & Cooling, product PG8MAA048110ACJA, Model PG8MAA048110 from Jully 2005
Inducer motor is coming on for a few seconds, several times in a row, then pausing. It does this with the thermostat set for either Off or AC. The exhaust vent does not feel warm, and there is no fwump-woosh of the burners coming on.
I captured a blink code of 22 that, according to the labels, translates to "Abnormal Flame Proving Signal - Flame is provided while gas valve is de-energized. Inducer will run until fault is cleared. Check for: - Leaky gas valve - Stuck open gas valve"
Before we get too wrapped up in gas valve codes, here is a little background. We had a rusted out drip pan in the old AC unit. The water leaked down onto the control board and fried it. (fan would not start) The leak was not fixed and probably continued to drip on the new board. Then the AC coil was replaced and everything is now dry. My guess is some damage had already been done.
Any thoughts on what to check next?
If I can figure out what wire/connector the Flame Proving Signal is on, and what voltages it should show, that seems like a logical place.
Is a control board cheap enough to use as a diagnostic part install?