I have a Heil furnace circa 1990 with an electronic intermittent pilot. when the furnace tries to kick on the ignition module fires and the pilot briefly lights for a split second. then all goes dead.
I've checked for voltage at the gas valve and have 24 volts on the two hot wires - one is only hot during spark off (or is it spark on, can't remember). the other on stays live when I unplug it, and there's a constant humming sound until i plug it back in.
anyway, it's as if the pilot gets a short shot of gas, then goes out. then the thing tries to fire again a couple seconds later, and just keeps repeating.
I don't see a thermocouple/flame sensor. but there must be one, right?
ok, after further research & troubleshooting I've found the following:
the gas valve (honeywell 8204) appears to have bad valve coils. I ohmed them and got infinite resistance. the identical set up for the 1st floor shows about 20ohm for both the PV and MV coils.
strange thing - the pilot does briefly light. and I've verified that there is definitely a shot of gas coming out of the pilot line (smell test) - not much, and it quickly dissipates, but it's there. and yet the coil appears to be blown. how's the gas getting out??
anyway, I feel confident the gas valve needs to be replaced. any tips on how to do this??