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I replaced my Lux thermostat with Honeywell RTH6360D1002 sometime ago and the heating worked very well. Now I am trying to use the AC and it is not working.

I removed four wires from my old thermostat (Red, White, Green and Yellow) and connected them to the the new thermostat - Red to R; White to W; Green to G; Yellow to Y; however, the air conditioning is not coming on.

In addition, I also have a blue wire coming from my unit that is not connected anywhere.

Appreciate your help. Things are heating up and would love to get the a/c running.

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    Can you post photos of the wiring at the air handler/furnace please? Jun 1 at 11:40
  • ThreePhaseEe, thank you. The problem was with the thermostat. I put a new one and it works like a charm. Thanks for your response.
    – Curius
    Jun 4 at 14:54
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The "Y" wire, which MAY be yellow but doesn't have to be, controls the cooling. You hooked color-to-color but that is not necessarily correct.

Go to the HVAC unit itself and look at the terminal that these wires are hooked to. Then check that you have function connected to function instead of color to color.

You may also need to check the settings on your new thermostat to make sure you have it programmed properly.

I will add that HVAC thermostat wiring is anything but standard. There is a general convention but many systems and installations different and you should never count on the colors matching the function.

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  • Thanks. When you say HVAC unit are you referring to the "Payne" furnace or the outdoor box with the fan?
    – Curius
    Jun 1 at 19:32
  • Hi jwh20, the problem was with the thermostat. I put a new one and it works like a charm. Thanks for your response.
    – Curius
    Jun 4 at 14:55

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