My Rheem 80 Plus Furnace from about 1985 is not starting when the thermostat turns system to on.
The part that looks like a solenoid(B) buzzes loudly when switched on. I previously put in a new exhaust fan(E) and vacuum hose when the old squirrel cage rusted out. I have an second identical system so I swapped parts to see if I could diagnose the problem. I tried swapping the board that has (A) and (B) and then the board that has (C) and (D). Neither worked. Anyone have any ideas?
Your suggestions would be greatly appreciated.
Yup, start with your transformer and make sure you have power around 24VAC. Next, be sure your draft inducer motor is getting power, exhaust fan as you call it. There's a temp sensor, a high temp safety sensor and heating surface igniter. Whip out your DVM and work from the simplest things to the more complex.