Is It Difficult to Change a Thermostat?

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  • Written By: O. Wallace
  • Edited By: Niki Foster
  • Last Modified Date: 10 November 2018
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Due to rising energy costs, many homeowners are opting to replace their old manual thermostats with newer digital, programmable thermostats. Experts estimate that the decision to update a thermostat can save a homeowner up to 35% in energy costs per year. Instead of maintaining a constant temperature for 24 hours a day, seven days a week, like a manual thermostat, a digital thermostat can be set to turn off during the day when the family is at work or school and to kick on when they come home. Different programs can also be established for weekends and evenings. Replacing a thermostat is usually not very difficult, and only requires a few common tools.

When purchasing a replacement thermostat, a homeowners should be sure to confirm that the new one is compatible with the home’s heating and cooling system. Although many people choose to replace their thermostat with a digital model, manual styles are available and are less expensive. Most employees at the local hardware store’s electrical section can help with this choice. The only tools required are a standard screwdriver, a drill, a level, and masking tape. For safety, many experts recommend wearing safety goggles when changing a thermostat.


As with any electrical project, a homeowner should always turn off the power first to avoid a shock. Although the wires in a thermostat are low voltage, it is smart to turn off the power before touching any wires. This can be accomplished at the fuse or breaker box, or a switch may be located around the heating and cooling unit. If the breakers are not individually marked, a homeowner may need to shut off power to the entire house.

The following is a list of step by step instructions on how to change a thermostat:

  • The homeowner should remove the cover of the thermostat.
  • Using masking tape, she should label the wires according to their screw terminal locations, then remove the wires from the screws.
  • She can then unscrew the body of the thermostat to remove it from the wall, making sure that the wires don’t fall behind the wall during this step.
  • New mounting holes for the new thermostat can be marked by holding up the base and marking the holes using a pencil. Once this is done, the homeowner should drill the new holes.
  • She should then thread the wires through the base of the new thermostat and connect them to the terminals on the base. When doing this, she must pay close attention to the wiring instructions or diagram of the new thermostat, as the color coding may not correspond from the old thermostat to the new thermostat.
  • The homeowner can then install the body of the thermostat to the base, and make sure to install new batteries if needed. Power can then be restored.

When a homeowner decides to change a thermostat, he or she is making the first step in updating an important system in the home. This is a relatively simple home repair, but as with any electrical job, if it becomes overwhelming or confusing, an electrician can always be called to finish the job. Once the job is finished, many older thermostats have mercury switches, making them hazardous waste. They must be disposed of properly, according to city ordinances.


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Post 3

@ GiraffeEars- I would like to add a couple of things. It may be best to change your cars thermostat when you are also doing a radiator flush. Since changing a thermostat already involves losing some coolant, there is no better time to do a full flush. You should also sand out the gasket sealant before inserting the new thermostat so you can get both the cover and base of the gasket housing. Your vehicle manufacturer often recommends doing both of these together every 48,000 to 60,000 miles. Good luck and have fun!

Post 2

@ Babalaas- There is a big difference, but it is just as simple. When changing the thermostat in a car, you can forget the thermostat wiring diagram. All you will need is a ratchet, a screwdriver, a new thermostat, a rubber seal, and gasket putty. If you are unsure of yourself, you can borrow a Chilton or Haynes manual for your vehicle from your local library.

Step one: Find the large hose on top of the radiator and follow it to the thermostat housing. Disconnect the hose and lift it above the radiator.

Step two: Undo the two to four bolts on the radiator housing, and pull out the old thermostat and o-ring. Replace these with the new parts exactly how you took them out, making sure the spring points down.

Step three: Use sand paper to remove any old gasket putty, reseal the housing cover, and replace.

Step four: Reconnect the radiator hose and top of antifreeze reservoir.

Post 1

Is there a difference in changing a car thermostat? My car seems to be running hotter than normal, and a friend told me it could be in need of a new thermostat. My brother said he would help me, but I want to find out the basics involved. Anyone?

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