Do-It-Yourself Thermostat Installation

How to Install or Replace an AC Thermostat

A thermostat is a small household appliance that regulates the function of your central air conditioning system. It is essentially a temperature-controlled switch that turns your heating and cooling system on and off, according to predefined temperature settings that you set. If your thermostat has become inaccurate, it is usually difficult to fix yourself, and can lead to higher utility bills. This article will show you how to repair your inefficiently functioning AC system by installing a new thermostat.

Things you'll need for this repair:

DIY thermostat installation tools




1. First things first -- SAFETY. On the main circuit-breaker panel of your house, turn off power to the circuit supplying your heating and air conditioning unit. This reduces the chance of electrical injury while you fix your AC system.

2. Review the manufacturer's instructions for the new thermostat that you've bought. Installation is generally similar across models, but it's always a good idea to familiarize yourself with any steps unique to your thermostat.

3. Remove the old thermostat by removing its front faceplate and accessing the screws that mount the wall plate to the wall.

Standard HVAC thermostat 4. Grab a pen for this next step -- you want to remove all the wires that connect to the old thermostat, while keeping track of which screw terminals they connected to. The terminals are usually labeled with the letters R, Y, G, and W, corresponding with the colors of the wires connected to them: red, yellow, green and white. Make a note or sketch to avoid confusing them later, then remove these four wires from the old thermostat.

5. Those four wires are loose now, so make sure they don't slip back inside the wall. Use a piece of masking tape to fix them to the outside of the wall.

6. Next remove the wall plate that attaches the thermostat to the wall. Make sure to unscrew all fasteners. Whew! The old thermostat is now off.

7. This step is the reverse of what you've just done. Installing your new thermostat begins with mounting its wall plate. The screw holes in the new wall plate probably won't line up with the existing holes, so use a pencil to mark their locations on the drywall. It's helpful to use a level here. Then drill the new holes, at an appropriate size for drywall anchors. Finally, push the drywall anchors into the holes until they're flush with the wall (a hammer may help).

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