What Do Thermostat Wiring Colors Mean? What Do Thermostat Wiring Colors Mean?

The colors of thermostat wiring indicate how each is used. To make sure that the thermostat functions properly, you have to make sure that all of the color-coded wires get on the appropriate terminals. While each system can vary, generally, you will find that the wires have universal coding:

  • The red wire is the hot side of the transformer.
  • The yellow wire deals with the compressor, which typically has to do with cooling.
  • The green wire is the furnace blower fan.
  • The white wire deals with the heat. 

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