As I am getting a little older, I'm getting lazy. Called Heating Repair to assess no heat from a BDP furnace. When told gas valve was defective, wife implored let him fix it. This was after $89 diagnosis fee not applied to $450 for valve. EF
32CW 183 replaced unit not working; now told igniter defective, then printed circuit board defective. As I am an elec engineer, I informed tech that multiple problems were not likely. Checked old solenoid coils have appropriate impedance.After throwing tech out, got off my ass and inspected furnace. Solenoid is clicking but no ignition. Checked wiring and by placing a little pressure on connector to printed circuit board furnace ignited and functioned normally for about ten days.
Then stopped working. Inspected again and cleaned connections with switch cleaner. Now, pilot ignites, small fan does not turn (I think this flue fan did before) and after 5 seconds or so instead of gas valve fully opening goes back to clicking solenoid. I think either the flue is not present due to the fan not turning or less likely, the bimetal is not reacting to the pilot flame.
I am an experienced hands on engineer who can fix anything, given adequate schematics. I understand safety. Can anyone explain the appropriate start sequence with voltages at appropriate locations? I have a pretty good general idea, and have worked on old furnaces before (my own). Thanks in advance for any help.