Trane XE80 Furnace Gas ignites intermittently

[westcoast]

Trane XE80 - My gas furnace only lights intermittently. The ceramic igniter heats redhot but starts to cool just as the gas is released and sometimes it does not light. It seems as if the timing is slightly off - the gas is released a little late and a sensor kicks in to say the gas is being released and not lit, so shut it off. The furnace will blow unheated are for a protracted period as if it thinks it is heating but the gas is not lit.

If it continues for a number of cycles it sometimes helps if I turn of the furnace and then restart it.

This is a problem that has been going on for a year or two.

Any advice is appreciated.

[ACtechGUY]

It is hard to say exactly what may be happening without knowing the how long each device is doing something.

A typical sequence is: draft inducer motor runs for about 10 seconds. then hot surface ignitor glows for about 10 seconds. The main gas valve then opens and woosh flame on. hot surface ignitor then goes off.

If no flame is sensed after gas valve opens then ignitor goes off and Blower comes on . Furnace tries to relight again after a short period.

The bad news is if the ignitor is not staying on for long enough , it is a problem with the fan control board .

If you look closely at the circuit board , you may see one or more electronic items damaged in some way or another.