Hello all! I have a Coleman Gas Furnace that is not working. For a
while the problem was intermittent, but now it completely quit. The
thermostat is working properly, sending the furnace the signal to
heat. The sensors and the igniter are working. The igniter glows and
is ready for the gas valve to open. You hear a click in the control
module and the gas valve does not turn on and the igniter shuts down.
We are torn between the control module and the gas valve being
defective. Any help would be very appreciated.
On Dec 4, 10:31 am, glitter email@example.com wrote:
Put a VOM on the wires going to the gas valve. If it gets voltage
when it's supposed to open, then it's the valve. No voltage, then
it's something else, most likely the controller. I'd also measure
the voltage with the wires disconnected, because if the valve
solenoid is shorted you could read zero or low voltage due to
the short. Voltage is usually 24V.
I agree with your answer, but I would add that it is not uncommon for
the coil on the gas valve to open up. He could put an ohm meter on the
coil connection with one wire removed to check the coil. I have had at
least two valves that had open coils.
On Sun, 4 Dec 2011 09:08:28 -0800 (PST), " firstname.lastname@example.org"
I would do the opposite - I'd test it with the valve connected,
because a high resistance connection would still show full voltage
when disconnected - and would show low or no voltage when connected. A
shorted solenoid is a much less likely situation - and can easily be
tested for with an ohm-meter.
On 12/4/2011 9:31 AM, glitter email@example.com wrote:
Would you happen to have the model number of your furnace? I may be able
to look up the wiring diagram or service manual online. If your
furnace is a later model, the problem could be something as simple as
a Klixon temperature sensor with a manual reset button. I found a good
example picture showing what a manual reset safety sensor looks like
and you'll notice the reset button between the Faston terminals. The
one you have may have a smaller black button and there may be several
mounted in different places inside the burner cover.
The model number is: 7970-656/D One thing my husband did do, he
hooked up a power supply to the gas valve while it was going through
the cycle and it opened to allow gas into the burning chamber. The
meter says it is getting voltage, so I am rather confused. Thank you
all for trying to help, you have no idea how much I appreciate it.
On Sun, 4 Dec 2011 15:15:24 -0800 (PST), glitter firstname.lastname@example.org wrote:
Was it connected when you checked the voltage? Like I said in a
previous post - a high resistance connection in the control circuit
will show full voltage when open circuit, and low or no voltage when
connected to the load (solenoid coil).I'm suspicious you have a cold
solder joint somewhere on the control board
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