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 a

- 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
light off.

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.

Workaround is:

- 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?

Thanks.
--
bill
Theory don't mean squat if it don't work.

Replaced by a pro and checked out completely

"bill horne" wrote in message
...
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 a

- 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 light
off.

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.

Workaround is:

- 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?

You REALLY need to call in someone that knows what they are doing. A gas
furnace is nothing the experiment with......

"bill horne" wrote in message
...
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 a

- 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 light off.

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.

Workaround is:

- 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?

Thanks.
--
bill
Theory don't mean squat if it don't work.

This is Turtle.

By what you say the gas valve not closing properly when turned off by the
thermostat. Well have the furnce running and then pull one of the 24 volt
control wires off the valve to cut the power to it. Then if it slowly closes and
holds a yellow flame for 5 seconds or so. You have a bad gas valve and the cure
is to replace it and not repair. Repairing gas valves went out the door
somewhere about the 1960's .

There is slow opening and closing gas valves but none will hold a yellow flame
for 5 second like you say and they working good. I would suggest you call a
service company to check it out and make sure it is the gas valve and may have
something else too wrong causing this problem.

TURTLE