How to Replace a Thermostat (with Pictures)

2024 Author: Samantha Chapman | [email protected]. Last modified: 2023-12-17 09:13

The thermostat is a tool that regulates the heating and air conditioning systems both in the car and in the home. Replacing an inefficient one helps you save money on your bills and, in the car, contributes to your safety on the road. In both situations, changing the thermostat is easier than you think. Keep reading!

Steps

Method 1 of 2: Replace a Thermostat in the Home

Step 1. Buy a replacement thermostat that fits your system

Check the compatibility list located on the back of the thermostat packaging. Most of those on the market are compatible with almost all types of domestic systems.

• However, if you have a very special implant, be aware that finding a replacement part can be tricky. Here are some options (the information can be easily deduced from the thermostat packaging):

  • "For one system only": models with this wording are able to control only one system (heating or air conditioning) and must be mounted when the two ventilation systems are separated.
  • "For two or more plants": are used for heating or air conditioning systems designed for minimum or maximum adjustments.
  • "To be fitted to the home power supply": they are used by connecting them directly to the power supply of the house (mostly found in old houses).
  • "For 24mV systems": used for fireplaces, wall or floor boilers.
  • "For zone HVAC systems": these models are mounted in homes to centrally control both heating and air conditioning, even in a specific way from room to room.

  

  Step 2. Read the manufacturer's instructions regarding the wiring of the new thermostat

  Most use a similar installation system: however it is always better to refer to the instructions and images on the package. Otherwise you risk being literally cold!

  Reading all the instructions is often boring, no one denies it, but it's a step you don't have to skip if you don't want to mess around. Read them carefully and study the images. You need to be sure you are following them to the letter

  

  Step 3. Remove power to the thermostat

  Turn down the switches that bring power to it, to the boiler, and also to the air conditioning system. This allows you to minimize the risk of electric shock when disassembling the old thermostat and installing the new one.

  

  Step 4. Remove the old thermostat from the wall

  Most models only need to be lifted up to detach it from the wall mount. Loosen the screws that secure the support plate, if present.

  • Some thermostats have a base and a second wall attachment. You have to disconnect the entire thermostat, both the actual instrument and the holder. You will need to expose the bare wall and electrical wiring.
  • If the cables are corroded and dirty, scrape them with a small knife until they shine again.

  

  Step 5. Check if the cables are very old when you unplug the thermostat

  This is the passage more important. Most thermostat harnesses are coded but in some cases, especially if the work has not been done by a professional previously, they may be coded incorrectly. To make sure you are doing it correctly:

  • With a piece of adhesive tape, label each cable with a letter that corresponds to that of the connection on the thermostat. If the blue cable is connected to connection B, then write "B" on the tape and attach it to the cable. Label any wires you notice, even those that aren't connected to the thermostat.
  • Ignore the colors of the threads, except those that are identified thanks to them. Thermostats that have been installed by hand do not comply with international codes so the colors may not match what they should.

  

  Step 6. Let the disconnected cables dangle from the wall

  Tie them together or tape them together to prevent them from falling back into the wall. A lost cable turns a simple household chore into a nightmare.

  Do you want professional advice? Wrap the cables around a pencil, its weight is sufficient to prevent the wires from re-entering the cavity of the wall

  

  Step 7. Mount the new support plate to the wall

  Use this as a template to figure out where you need to drill the screw holes. If necessary, help yourself with a spirit level. Drill holes in the wall and screw the plate into place.

  • If your new thermostat has a mercury tube (i.e. it is a very old model) know that it must be mounted perfectly in line, otherwise you will not be able to get reliable temperature readings. A spirit level is therefore essential and not just for aesthetic reasons.
  • Make sure you drill holes of the correct diameter, usually 4.7mm screws are used.
  • If the thermostat is already sold with screws and anchoring hooks, be sure to use both.

  

  Step 8. Connect the thermostat to the cables

  Use the notes you took or the labels on the wires to find out how to reconnect the wiring. You can curl the wires around the thermostat connectors or follow the instructions the manufacturer included in the package.

  • The new thermostat should now have the same coding as the old one, unless the enclosed instructions indicate something different. If in doubt, call an electrician.
  • Some models are simply wired two-way, while others go up to five. If you have a lot of empty ports or connections don't worry, your thermostat should still work.

  

  Step 9. Secure the thermostat to the wall

  Put the cables back into the cavity, place the thermostat flush with the wall and slide it onto the support plate. Slide it down so that the anchor notches (or screws) hold it firmly.

  If your thermostat is mounted in an unsuitable position (for example near heat sources or drafts that affect the reading), then you must contact a professional to have the wiring moved

  

  Step 10. Turn the power back on to the thermostat, boiler, and air conditioner

  Be sure to flip up the correct switch in the general electrical panel. Wait a minute for the power to reach the instrumentation.

  Don't forget the batteries! Most thermostats need 2 AA batteries to work. Make sure they are not old and that you have inserted them with the correct polarity

  

  Step 11. Check the system to make sure you have done a good job

  Set the thermostat so that the boiler and air conditioning turn on at different times. Leave them on for at least 5 minutes. If your thermostat isn't working as it should, retrace your steps to check what mounting mistake you made.

  You may need to press the reset button on the new thermostat. Some models don't start until you proceed with this action

  

  Step 12. Program the new thermostat

  Each model is different, so you should read the manual if you have any doubts. Remember that programmable thermostats allow you to save a lot of money, the house will be cold when you leave but when you return it will be warm. It will turn off the heating / cooling system when you are not at home, saving you electricity and money!

  Method 2 of 2: Replace a Thermostat in Car

  

  Step 1. Make sure the car is cold

  It won't be a good day if you burn your hands and face, so make sure the car is cold before opening the hood and starting work. Wait at least an hour after turning off the engine before proceeding.

  It is not a bad idea to wear protective gloves and goggles. If you don't want to find your hands and face dirty with a slimy substance, it is better to opt for protection. Obviously, wear clothing that you don't mind getting smeared with grease and oil

  

  Step 2. Drain the antifreeze from the car

  The thermostat and the radiator hose are connected to the car's cooling system; if you don't get rid of the antifreeze you will end up with a lot of liquid dripping all over the place as soon as you start taking apart the pieces. Here's how to proceed:

  • Place a bucket (or similar container) under the radiator. You should have 1-2 liters of liquid to drain, so get a large bucket.
  • Under the radiator there should be a screw or a drain valve. Turn it to the left to open it.
  • Wait for all the coolant and water to come out of the radiator, put the valve cap or screw in a safe place where you can't lose it.

  

  Step 3. Locate the thermostat

  Each car model is different; some thermostats can be seen at first glance, while others are hidden in some crevice of the engine compartment and you have to look for them a bit. If you find yourself staring at the inside of the hood with a bewildered look, locate the radiator hose and follow it to the end, you'll come to the thermostat.

  • The body of the thermostat is probably a metal object with a gold color in the center and a rubber ring at the edges. It has the shape and size of a square spinning top.
  • If in doubt, consult your vehicle's maintenance manual and find the exact spot where the thermostat is mounted. This way you avoid putting your hands where you could injure yourself.

  

  Step 4. Remove the radiator hose from the thermostat housing

  Most of the time this tube is fixed with a clamp, just unscrew it and set it aside. Now access the crankcase to get to the actual thermostat. You will need a screwdriver and pliers for this operation.

  • Most vehicles have a closed crankcase with two or three bolts.
  • If corrosion or dirt has built up, clean it before inserting the new thermostat.
  • When you unplug the hose, some water will probably come out. This is completely normal.

  

  Step 5. If desired, test the thermostat

  It is possible that it is fully functional and that it is just blocked. Alternatively, there may be another component in the vehicle that has problems and is interfering with the performance of the thermostat. If so, it's best to test the thermostat. Here's how to proceed:

  • Get a pot of boiling water.
  • Put the thermostat in the water. The instrument should open around 88 ° C, as water boils at 100 ° C should be more than enough.
  • If the thermostat doesn't open in the water (and closes when it cools down) then it's broken and you need to replace it.

  

  Step 6. Change the old thermostat to a new one

  This is a simple operation, you just have to reassemble the new one exactly like the previous one. If you can, put the rubber ring back on to seal the edges.

  If the inside of the crankcase is dirty, clean it first with a detergent. To extend the life of the thermostat to the maximum and not have immediate problems, it is advisable to place it in a clean casing

  

  Step 7. Reassemble the cooling system

  You remember the procedures you've followed up to now, right? Here is a brief reminder:

  • Make sure the thermostat is in place and secure.
  • Screw the cover onto the thermostat. At first screw the bolts with your hands and only then tighten them with pliers or a socket wrench. Be careful not to strip the bolts.
  • Refit the radiator hose with its clamp. The hose must fit on the outside of the casing and the clamp must be tight and closed.

  

  Step 8. Put the coolant back into the radiator and make sure there are no leaks

  If the liquid you drained earlier was pretty new, you can reuse it. If, on the other hand, it was old, it is advisable to take advantage of it to replace it. In both cases, make sure the radiator drain valve / screw is closed before refilling.

  Once the liquid is poured, check for leaks. Your car needs coolant to run safely. If you notice any leaks, know that you won't go very far

  

  Step 9. You can get back behind the wheel

  Now you need to monitor the thermometer in the cockpit. If it works, still do several tests to make sure everything is perfect. If you notice any problems, you will need to see a mechanic as there may be malfunctions with other components.