How to Replace an Old Thermostat

Hi, I’m Jeff  and in today’s video, I’m going to show you how to replace an old thermostat. Maybe you’ve got one that’s ancient and just needs to be replaced or you’ve got a newer one that went kaput, like the one I’ve got here – it’s a digital thermostat, and it no longer works after 10 years, which is a bummer. But the good news is it’s super easy to replace an old thermostat that’s not working anymore. So let’s get to it. Of course, before you do anything, turn the power off to your heating and cooling system. Here’s my old thermostat; it turned off ‘cause it was hard-wired. And I’m going to wire up a new Honeywell thermostat. It’s RTHL2310, and it’s real simple. All you have to do is tilt the old thermostat forward and pull it off the base plate. Typically, there’s a pin connector that holds the thermostat to the base plate along with four clips.

If you have an old thermostat with mercury, dispose of it properly. Take a picture of your existing wiring. That’s going to help you wire the new thermostat. But also, take note of how the wires are wired. And you’ll want to label them with the appropriate labels. As you can see here, I labeled the green wire with the G sticker. And the rest of the wires I labeled according to the old configurations. So that’s why the blue wire has a W2 sticker on it. Remove the screws that hold the base plate to the wall, and then carefully – when I say carefully, I mean very carefully – hold the wires with one hand and pull the base plate off the wall.

You don’t want the wires to go back behind the wall; it’s a real pain, and that’s why I put a vice grip set of pliers on the wires to hold them in place. Drill holes in the wall that match the base plate, and put some blue tape on the wall to catch any of the dust. Place the blue inserts into the wall. Pound them into place with a hammer or the base of your screwdriver, like me. Carefully feed the base plate over the wires. And you may have to trim any of the wires coming out of the wall – that’s what I had to do here. And then unscrew the small terminal screw using a precision screwdriver. Stick the wires into their corresponding slots, and then tighten down the terminal. Remove the vice grip, and here you go. Here’s the wiring. I put the blue with the blue, G with the G, yellow with the yellow, W with the white, and R with red. Secure the base plate to the wall. Remove your blue tape with all the dust on it – I just simply did that over the thermostat box that came with the Honeywell thermostat.

Put the batteries in. Remove the sticker. And then make sure that this switch is set to either GAS OR OIL or ELECTRIC. I have an electric furnace. Press the thermostat down onto the tabs. And you’re almost done. You have to set the time for all programmable thermostats. Set the time. Hit the run button, and you’re good to go. Now, the last thing you need to do is set up the Heat, Off, or Cool, and then set the Fan to either Auto or On. Well, there you go. That’s how you replace an old thermostat that’s not working anymore.

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