How to Change the Thermostat on an AC Unit
- 1). Turn off all power to the heat and air in the breaker box.
- 2). Remove the outside cover from the thermostat and expose the sub base. It will look like a circuit board with four wires going to it. There should be a red wire labeled "R," a green wire labeled "G," a yellow wire labeled "Y," and a white wire labeled "W."
- 3). Disconnect these wires from the sub base and unscrew it from the wall.
- 4). Place the wires through the hole on the new thermostat's sub base and mount it to the wall.
- 5). Connect the wires back to the sub base, red to R, green to G, yellow to Y, and white to W.
- 6). Attach the new thermostat's cover to the sub base, then turn the power back on.
- 7). Test the new thermostat by setting it to auto and cool, then turning it down until it comes on, then setting it to auto and heat, and turning it up until it comes on. When set to heat, most furnaces will delay before they come on, so wait up to four minutes to see if it comes on.
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