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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Lennox gas gas furnace G14D3-80-CS / the Thermostat would be

Customer Question

Lennox gas gas furnace G14D3-80-CS / the Thermostat would be set at 68 but the heat will not come on untile it gets around 60 then it will stay on until it gets 78 then shout off . I changed the Thermostat the furnace will not start now. What is wrong the power is on and I have reverts the wires and it stil won't start checked fuse in furnace its good
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.


The old thermostat was probably bad, and you probably made some sort of error when wiring the new thermostat.

I need the brand and model number of the new thermostat... and which color wire is attached to each of the terminals on the new thermostat.

Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip-icon at the right end of the toolbar at the top of this dialog box,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If there is no paper clip-icon, look for the '+attach files' link at left of your send button.

I can mark it up with trouble shooting instructions. You will need a multi meter ($30 at a hardware store) and some experience working with appliances, let me know a lot about your skill sets in those regards.