This is a York model G80C075120 Exterior forced air heater.
The blower, igniter and fan work, the main burners ignite but then shut off 5
seconds later; cycle three times and then shut down.
There is no error code.
I’ve replaced the flame sensor
Purged the gas valve, measured 9v from the control board on the two leads
Re-inserted all the leads to the control board to insure good contact
and bypassed the thermostat by leaving the ground attached and connecting the
call for heat and blower wire twisted together with the same results. What
am I missing ?
i do not have your furnace. here are some thoughts:
gas boiler burner problems i've has: i had to replace the pilot
assembly and adjust the pilot flame to properly surround the flame
different problem: replacing gas valve was required.
you must refer to your service manual on this problem and the service
pages of your furnace's components.
If the polarity of the incoming power is reversed you will still have
120 volts between black and white and the furnace will do exactly as the
OP described. I have seen it happen before-- more than once. Make sure
the black is hot and the white is neutral. Around here, about 99+% of
furnaces are connected with a pigtail and receptacle, so the polarity
can be accidentally switched easily if anything is done anywhere in the
circuit. Most furnaces will run ok during a/c use that way-- it will not
show up until the heat is fired up. Larry
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