Have HVAC Questions? Ask an HVAC Expert for Answers
Welcome, my name is XXXXX XXXXX I will do my best to help you with your issue.
Do you have a strong pilot?
Then you may have a faulty gas control valve. Aside from a weak pilot that would get blown out when the burners shut down a faulty gas valve on a unit of this age is the most likely culprit
There is one other rather unlikely possibility
If there is a terminal block between the thermo and the gas valve or limit terminals on the gas valve then a tripped limit could also cause this
Actually the limit wouldn't be connected to this type of terminal. It more likely a spill switch or an overtemp sensor
Thats what I was thinking also but didnt want to waste time or money changing if there was something else simple I was missing. Cause really not like a lot of other moving parts. And I know the wall thermostat works cause when air cond runs it works fine. Plus the pilot would not go out if it wasnthe stat. So I eill try replacing gas control box.
Just check for the terminals I mentioned in my last comment
before you spring for a new valve
If these "safety sensor" terminals are on the gas valve they would be entirely separate from the 24 volt terminals that power the valve
2 terminals with leads connected to a temp sensor
Not a common config but it is a possibility
Do you have any more questions?
Im looking at furnace now to check sensors
Ok so I cleaned off one sensor on upper plenum area and relit pilot and am running furnace to see how long will run and if runs the cycle if pilot stsys lit this time
That doesn't sound like what I was referring to. I'm not talking about the limit switch/control. The limit would shut down the burner but not the pilot. I'm talking about a sensor with leads connected to the gas valve (not the 24 volt circuit) or a terminal strip attached to the thermocouple.
So far still running. Yes is a sensor two wires from wherethermocouple threads into to thetwo term sensor attaches to frt chamber area. Only other wires from gas valve go to connections by where thermostat wires all hook up at transformer
That could be the problem. Try jumping the terminals
You could have a bad sensor or your unit may be getting too hot
Ok furnace just ran the cycle and shut down and the pilot stayed lit.
So looks like we figured it out. Any more questions?
Will keep an eye on . If any more trouble will try those sensorss first. Thanks