furnace broken

[matthew NYC]

I have a four year old forced air atwood furnace. The blower comes on and the furnace ignites for about five seconds than cuts out and tries again but never catches. I have a three month old regulator and full tanks of gas. All other gas appliances work fine. Any ideas?
thanks matthewNYC

[Pat370]

Matthew, I am not for sure but this sounds lihe a bad
electronic control board to me. If you remove the board
most any good RV repair service center should be able
to test it.


Good luck,
Pat 370

[Tinsel Loaf]

Do you have something blocking the output vents causing the sail switch to not open alway way? Check the voltage on the gas solenoid valve to see if it has voltage during the spark causing the gas valve to open. Sounds like lack of fuel passing the spark.

[Pat370]

Tinsel Loaf, As I read this post he says that the furnace does lite and run for about 5 seconds and then shuts down. This would indicate to me that the sail switch is
operating ok and the unit is getting gas.

Thanks,
Pat370

[Tinsel Loaf]

According to the manual the VC or valve control comes from the black wire on the control board to ground allowing gas to pass in front of the electrode. There is the LS or limit switch that is before the SS or sail switch. There should be 12 volts from the LS and SS sail witch to ground for the controller to turn the main valve on. If the TH or thermo relay is open you will not find the 12 volts at the LS or SS that means the thermo relay is faulty causing no VC action.

[Tinsel Loaf]

If you have an led on the board this is what the flashes mean:
LED: Steady on, on flashing = internal PC board failure.
LED: 1 flash with one second pause = Limit switch/airflow problems.
LED: 2 flashes with three second pause = Flame sense fault.
LED. 3 flashes with three second pause = Ignition lockout failure.