HVAC Questions? Ask an HVAC Expert for Answers ASAP
yes the parts are available.
The initial test will be to see 120v is present terminal L1 and Neutral
Then if 24v is present from transformer on SEC1 and SEC 2
Then if all is ok...24v between terminal R and C at thermostat wire connections.
Between sec1 and 2......sec 1 is 24+ and sec2 is 24-
one lead to each
Now check terminal R with one lead and terminal C with other. Should = 24v +
Then with stat turned up W and C = 24+
Use a short piece of wire or taped paper clip shaped in a U and touch the R terminal o the W terminal. Or if possible...actually screw it into place thus jumping R and W
Is the exhaust fan running?
There is a plastic plug that goes to the exhaust motor. Unplug and see if the 2 prongs in the supply side of the plug has 120 volt.
Upper section by motor is a round air switch with a rubber tube to it. Behind this switch is a small square circuit board that has 3 wires that attach to the round switch. Do you know the part and location I refer to?
That is called and inducer circuit board.
Turn off power and remove the pressure switch to access the little board. See if there is a "hot spot" at about 2:00
Plug all back in, tap pressure switch to make sure it is not stuck. Then locate the wire that comes from the limit to the small circuit board. The wire that comes to the circuit board from the limit switch should have 24v with meter lead to it and one lead to cabinet
This switch here behind the gas valve
Sorry, you have first generation then.
But you should have an input to the small board from the big board
On main board...check LIM2 with one lad and the cabinet or ground with other lead.
Thank you...remember that one well. Have you removed the left side edge connector and checked the contacts?
I did not have you check limits because the blower would be blowing....We know the transformer is ok.....It is either the main board or the inducer board. Just to cover the bases...jump out each limit and rollout.
The limit is what is on the front wall behind the gas valve. Here are the ones you would
another test at this time since you smelled something hot....with power on and door switch taped down....touch the R and the G terminal together and tell me if fan kicks on
Thanks....well it is definitely circuit board related. It may sound rudimentary...but do either board have the sulfur smell?
The upper circuit board is the main suspect...to be sure, check edge connector wiring on the schematic to the furnace....locate 24v feed from edge connector to the inducer relay.
24v present= bad inducer board.
No 24v = bad main board.
I see your version has the 3 wire pilot...
for sake of eliminating ......hit the side of the pilot assembly to make sure it returned to normally closed. I will be online off and on today to see how it is going.
our blower motor runs with R and G so that is good....can you get 120 v to the inducer motor for test?
I do not have resistance values....but the 3 wires going to pressure switch work by running 24v to switch an out on nc...then on start up 24v should appear on n.o.