How to replace a thermostat in 4 steps

How to replace a thermostat in 4 steps



Your thermostat plays a critical role in your home. It might look like a small wall fixture, but it controls when your heating and air-conditioning systems kick on, which means it controls the comfort of your home.

Therefore, when the thermostat breaks, it can cause tremendous problems for homeowners. We will explore what you need to know about replacing a thermostat and key signs you can watch for that indicate your thermostat no longer works as intended. Here is what you need to know.


Can you replace a thermostat yourself?

Thermostat replacement and installation is a DIY project that some homeowners can manage if they have the experience and understanding necessary to manage the wiring and electrical components. However, those without the necessary DIY experience may find hiring an HVAC contractor significantly easier and safer.


How do you know a thermostat is bad?

A home without a working thermostat can quickly become uncomfortable. If your heating or cooling system does not turn on properly, it’s important to evalwwwe whether there’s a problem with your entire HVAC system or just your thermostat. Fortunately, you can explore some common signs and symptoms of a malfunctioning thermostat, which will help you determine if the problem arises from your thermostat itself. If you see any of these problems, you first want to check your thermostat.

  • You do not see any power going to your thermostat. If your device does not tell you standard information, such as the room’s temperature, that is a good indication that something is wrong with your thermostat.
  • Your HVAC system will not turn on or off as needed. If your thermostat malfunctions, such as due to a problem with the internal wiring system, it will not send appropriate signals that tell your unit when to turn on or off.
  • Your system appears to be short cycling. If the HVAC system short cycles, it will keep turning on and off without reaching the target temperature. This issue can happen because of miscommunication between the thermostat and heating or cooling system. It will quickly wear out the parts without making your home comfortable.
  • Your thermostat does not seem to respond to temperature adjustments or forgets preprogrammed settings. If you adjust the temperature and do not hear the click of the heating system responding within a few minutes of the adjustment, or settings you made before seem to have disappeared, your device may be malfunctioning.
  • The thermostat does not get an accurate read of your room. If the thermostat lists a temperature you know to be wrong for the interior of your home, it will throw off your entire HVAC system because it will not know when to turn on or off to warm up and cool off the space.

These signs indicate that you may want to consider replacing your thermostat with a new device.


How to replace a thermostat in 4 steps

Replacing a thermostat can offer several advantages. Those with a malfunctioning thermostat will find that this home improvement project will get their HVAC system to work properly again. Additionally, some homeowners may wish to upgrade their device to improve their energy savings. A programmable thermostat or a smart thermostat, for example, can also be more energy-efficient. It can help the system better respond to the homeowner’s needs and cut down on heating and cooling when not needed, which reduces energy bills. For example, you can program it to not turn on during the hours when everyone is out of the house. The key is getting the right thermostat based on your home’s specific requirements.

If you have realized that your thermostat is the source of your HVAC problems, or if you simply want to upgrade your thermostat to a newer model, we will walk you through how to replace this handy device. 

Before starting, make sure you have the following items on hand:

  • A new thermostat
  • Access to your main electrical panel or breaker box
  • A screwdriver
  • Masking tape
  • A level
  • Fire-resistant insulation
  • Your manufacturer’s instructions for your thermostat type, in case you run into problems with your new home thermostat

Step 1. Turn off the power supply

First, turn off the power to your existing thermostat. If you go to your main service panel, you should find the circuit for the thermostat clearly labeled. You want to make sure the power is off before starting any work that involves manipulating the wires.

While you disconnect the power, you also want to take a moment to verify that the voltage recommended by the thermostat manufacturer aligns with the voltage of the circuits you will use. Putting a higher-voltage device on a circuit intended for lower-voltage devices can be dangerous and even a fire hazard.

Step 2. Remove the existing thermostat

Once you have successfully disconnected the power to your thermostat, you want to remove the old unit. You need to first remove the old thermostat plate and then remove the thermostat body. 

As you remove the former unit, use this opportunity to label the wires with masking tape as you disconnect them. This tip will help you remember their screw-terminal locations so reconnecting the new unit is easier. Use a system of labeling that makes sense to you.

As you disconnect the wires, tape or otherwise prevent them from falling back into the wall.

Step 3. Install and wire the new thermostat base

Now you will start installing your new thermostat. 

  1. Separate the thermostat base and cover. 
  2. Carefully thread the required low-voltage wires through the labeled openings on the new base. 
  3. Use your level to make sure the unit is perfectly straight.
  4. Once you properly align the unit, use screws to attach the base to the wall. 
  5. Properly position the low-voltage wires in the screw terminals on the base and connect them.

If you need help troubleshooting your thermostat’s wires, your owner’s manual can help you verify where all the wires should be.

Step 4. Mount the new thermostat and power it on

Once everything has been properly installed, push any extra wiring into the hole in the wall and plug the area around the wires with some type of fire-resistant insulation. This will help improve the accuracy of the thermostat.

Then connect the control-unit portion of the thermostat back to the base with your screws. Once you have finished installing the thermostat, restore power to your HVAC system and your thermostat. You can then begin to program the thermostat based on the instructions for your specific model. Test to ensure the HVAC system responds properly to the thermostat and everything cycles on and off correctly.

Bonus: Install a C-wire for smart thermostats

If you have decided to install a smart thermostat in your home that connects to your Wi-Fi and other smart devices, you will have special considerations. Specifically, you will need to properly install the C-wire, or common wire. This wire is responsible for maintaining a regular flow of power to the thermostat without disrupting your use of other appliances.

  • If you used a smart thermostat previously, first look and identify the C-wire as you disconnect the old one to make sure you properly label it so you can reattach it.
  • If you did not use a smart thermostat before, look at the wires in the wall to see if you have an unused C-wire. You can also look at the HVAC system itself. Examine the control board to see if there is a C-wire. If you find one, you can use the other end for the thermostat.

If you do not have a C-wire, you have three main options. 

  1. If you have a C terminal on your HVAC control board, you can install the wire and run it to the thermostat. 
  2. You can use a 24-volt adapter with a C-wire that you plug into an outlet near the thermostat. 
  3. You can use an add-a-wire kit and follow the instructions.

If you have trouble getting the C-wire connected, reach out to an electrician to help you safely add the wire.


Protect your home systems from costly repairs with Cinch

As you work to protect your home and keep it comfortable with a properly functioning thermostat, you want to make sure the rest of your HVAC system is also well-protected. 

With Cinch Home Services, you can find plans that help you safeguard against problems with your critical home appliances and built-in systems, including your air conditioner and the rest of your HVAC system. Learn more about what Cinch warranty plans can offer and get started protecting your home by exploring your options right here. Reach out today for an instant quote


Replacing a thermostat can help keep your home comfortable. Here is what you need to know about replacing a defective device.

Your home protection is ready and waiting!