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After installing a Google Nest, my furnace heats until it reaches the correct temperature, but if it sits, the controller light turns off and I need to turn the breaker off and then back on in order for the furnace to kick in. The controller light turns off, but does not flash as far as I have seen. I have switched back to the original thermostat, some basic Honeywell one, and it works fine. There is a C wire connected, though I had to add that and I'm not sure if it's totally legit. Currently the C-wire is connected at the T terminal.

My furnace is a Lennox G14 series (I'm not sure which model exactly).

I am fine using the old thermostat, but I am bummed because I was looking forward to automating this stuff. Thanks for any help!

Wire diagram

Thermostat wires connected to furnace

Controller with light on

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  • can you show us the problem maker (Nest) wiring
    – Traveler
    Nov 11, 2022 at 18:54
  • where did you get the C wire from ?
    – Traveler
    Nov 11, 2022 at 19:10
  • @Ruskes I never took a picture of the Nest wiring, but all the wires went to their respective letters (i.e. Red => R), and the blue wire went to C. I pulled the new wire with the blue included awhile ago, and the original thermostat is using it now. Nov 11, 2022 at 21:04
  • I am interested in helping you, but need more information. What was connected on Nest ? R, W, Y, G, C ?? What would shut down the furnace ? The Limit switch ! / why ?
    – Traveler
    Nov 11, 2022 at 21:35
  • @Ruskes R, W, Y, G, C were all connected. The furnace would reach the correct temp, turn off, and then most times not come on again, with the inside temp being 5-10 degrees below the setting. That's when I would have to cycle the breaker, which would turn the furnace on immediately. Nov 11, 2022 at 21:54

1 Answer 1

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The solution that seems to be working so far is adding a 1kOhm 5W resistor between W and T, that being the call for heat voltage. After contacting Johnson Controls, I was redirected to an engineer at Baso (which now owns this particular model of Johnson Control) told me that older controllers sometimes expect more of a load when heat is called for, and newer controllers have these built in.

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