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Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 19533
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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I have an old Gaffers & Sattler gas furnace. Pilot light is

Customer Question

I have an old Gaffers & Sattler gas furnace. Pilot light is on and the thermostat is working(clicking noise) but the furnace does not come on.
Submitted: 1 year ago.
Category: HVAC
Expert:  Rick replied 1 year ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

The first thing to try is to turn the power off then connect the leads on the R & W terminals on the thermostat. If you don't have terminals designations and only have 2 wires connect them together then turn the power back on. If that doesn't work then turn the power off again and try connecting those 2 terminals on the furnace with a short piece of wire. Then put turn the power back on. If you still have no response the you'll need a multi-meter to troubleshoot this any further.

Expert:  Rick replied 1 year ago.

Sorry for the misplaced text at the begging of my response. I've corrected it. We can proceed when you're ready

Customer: replied 1 year ago.
Thermostat is working because I hear the clicking sound.
Expert:  Rick replied 1 year ago.

That doesn't indicate anything other than it's the contacts are closing. It doesn't mean it's actually closing the thermostat circuit. If you want to get to the bottom of this then the place to start is with my instructions.

Customer: replied 1 year ago.
I did what you said. Still does not work
Expert:  Rick replied 1 year ago.

Did you try both options? at the furnace as well? If you did then you need a multi-meter to troubleshoot this further. Do you have one?

Customer: replied 1 year ago.
I did. No I do not have Multimeter.
Expert:  Rick replied 1 year ago.

Then there's not much more you can do. One other thing you can look for is rollout switches above and just outside the burner chamber (see attached picture for a typical one). You can try pushing the small button in the middle of the 2 wires. If it clicks you have reset it and the burner will fire up with any luck.

Customer: replied 1 year ago.
I do not see any rollout switch on this heater. There are two wires from the thermocouple. One goes to the Transformer and the other to the Gas valve. Then the red wire from the thermostat connects to the gas valve and the brown wire from the thermostat connects to the transformer.
Expert:  Rick replied 1 year ago.

This is a really old furnace if it has a thermopile (what you're describing). The most likely cause of the problem you're describing is a weak thermopile. The thermopile generates all the power (less than 1 volt) to operate the gas control valve. It does this when it heats up. When they get weak they don't produce enough voltage to make the round trip to the thermostat and back. We would replace thethermopile first in a case like this

Customer: replied 1 year ago.
I gave you the Make and Model number so you can give me the right advice. I thought it would be the Thermocouple or Thermopile but wanted to know if there was anything else an expert might know that I don't. I will go to the store and get one and try it. Thanks for your help.
Expert:  Rick replied 1 year ago.

You're welcome. Your unit is far too old for there to be any available specs on it. You described a thermopile not a thermocouple.

Customer: replied 1 year ago.
Rick, just to let you know that I just fixed the furnace by taking out the thermocouple and cleaning it with a wire brush(suggestion online by someone - Free) I thought you might want to know.
Expert:  Rick replied 1 year ago.

You still need to replace it. Wire brushing it off is a stop gap measure at best. It will fail probably at the least convenient time, like when everything is closed and you can't get parts. It's not a good idea to go into the Winter with an old thermopile that's already been acting up.