What are the colors for the different wires in a room thermostat? What are the colors for the different wires in a room thermostat?

Changing a room thermostat is not typically dangerous, since the electrical current supplied to these devices is usually low voltage. Once you remove the thermostat face plate and find the terminals, just locate the terminals and wires connected to them.

Thermostat Wire Colors

The red wire is usually the power wire. Be sure power on this wire is low voltage before working on it. If you are unsure, disconnect the power.

The yellow wire is for the air conditioning circuit. It should be connected to the compressor relay.

The white wire is used for heating and should be connected to contact that connects to the furnace.

The blue wire is generally not used and should be put aside.

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