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furnace boards

This is my furnace board. I don't see anything with a C terminal. Are there any connections on this board that I can use as a "C" terminal?

Below is the thermostat I'm trying to hook up. This is how it was wired at my old house.

Is this wiring correct?

  • Furnace Board R to Thermostat 24RH
  • Furnace Board terminal between R and W to Thermostat 24V Com
  • Furnace Board W to Thermostat W1
  • Furnace Board Y to Thermostat Y1
  • Furnace Board G to Thermostat G

Thermostat

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2 Answers 2

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It's the terminal between R and W

See the white wire coming from the cable to the A/C compressor? Since the red wire in that cable goes to the Y terminal, the white wire in that cable has only one place it can go for the A/C to work, and that is the C terminal on the control board or its equivalent transformer terminal.

P.S. as to how you have the thermostat hooked up? It's spot on.

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  • it's not well secured and seems milimeters away from popping out. Nov 6, 2017 at 9:21
  • Do mind checking my proposed wiring to the thermostat, and let me know if its correct?
    – Matt Miley
    Nov 6, 2017 at 16:40
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The documentation for that control board can be found here

ST9160A-C Electronic Fan Timers - Honeywell https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-1057.pdf

As @ratchet freak mentioned, the wiring needs to be redone. The inside of a furnace is noisy, dusty and subject to vibration and temperature variations. Loose connections create problems that are difficult to diagnose.

The end of the wires should be fashioned into a reversed question mark so they hook properly to the screw terminals.

https://www.hunker.com/13414272/proper-technique-to-wrap-an-electrical-wire-around-a-screw-terminal

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  • Do mind checking my proposed wiring to the thermostat, and let me know if its correct?
    – Matt Miley
    Nov 6, 2017 at 16:40

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