I have a 20-year old Carrier 58SS furnace with a 646A-X gas valve
converted for LP. Beginning at the point in the heating cycle when
main burners are burning, the symptoms are:
- When the thermostat is satisfied, the main burners turn almost off,
but continue to burn for about 5 seconds with much reduced vigor, and
with 2-4 inch orange flames burning vertically from the orifices.
- the pilot continues to burn, but also with a much smaller flame.
- later, when the thermostat calls for heat, the main burners never
Troubleshooting revealed the following:
- if the gas supply is turned off, the pilot, of course, goes out,
and if the gas supply is turned back on, the pilot hisses.
- when the thermostat is satisfied, and the main burners go nearly
out, I turn off the gas supply and the thermostat.
- when I want heat, I turn on the thermostat, the igniter starts
sparking, and I turn on the gas supply. The pilot ignites, and in
less than a minute, the main burners ignite normally.
I speculate that the gas valve is not closing completely when the
thermostat is satisfied, and if I'm correct, can the valve be fixed
(cleaned?), or must it be replaced?
Theory don't mean squat if it don't work.
Click to see the full signature.