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Remove power venter and inspect inside for damage
FYI. 3 flashes means pressure switch not closing.
I will let another expert try to help you
Does the exhaust motor run during this code?
and have you checked vent pipe/chimney for any blockage>
do you mind a short hands on test?
do in this exact order:
remove the 2 wires from pressure switch
hold wires apart
AFTER the exhaust motor starts put the 2 wires directly together metal to metal and hold.
you may find a small nail or wire shaped in a U handy to insert into the wire connector ends.
Tell me if the ignitor starts.
as soon as the wires from the pressure switch connect the inducer shuts off?
Does your induce motor wiring come from the gas valve?
Thank you. The only thing that interacts the pressure switch with 120v motor is the control board.
Can you get me the number from the control board or a pic?
very bottom of board center/left is a small black button....with power on hold that button in for 5 sec.
put all wires back in place and tell me if same issue remains
Then you have a bad circuit board.
The interaction between the 24v signals and 120v relays on the board are defective.
Only fix is new board.
you can shop around with the model.
Then one of the test prior was not done correctly when we bypassed the pressure switches.
Can you post a pic of the diagram on the back of the blower door?
on the back wall is a limit switch...flat against back wall...has a white wire on one side and a brown and violet on the other...the violet leads to pressure switch.
Do you see this violet wire
Keep this handy
now the violet goes to the pressure switch and then out the other terminal...you will see where I drew arrows...that there are 2 "if used" switches.....can you tell me what the violet wire goes to before it goes back to circuit board or show pic of it?
oh boy...a hidden auxillary limit...reach back there and press the center and see if it clicks
there is usually a bump plate over the switch.
remove the 2 wires....pull them out to where you can work on them.
Cut ends and twist together and tape. (this is a redundant limit if the unit were upside down...)
Can you try this now?
you see the furnace is multipoise.....those are there to cover if you had the furnace horizontal or vertical downflow....I assume yours is a standard upflow?
if 2 bypass both...we only need the one up above burner