How To Tell If Your Thermostat Is Broken

How to know if your car or home thermostat is damaged. A thermostat is a small box that is installed on the wall of the house and connects to the heating and cooling system.

It measures the temperature in the home and controls the air conditioning and heating. If the system does not turn on, or has sporadic failures, the problem may be the thermostat.

How To Tell If Your Thermostat Is Broken

No, you do not have to be an HVAC technician or call one just to check what the problem with the system could be. You can check it to make sure it has been damaged before calling a professional. Here’s a step-by-step guide on how to tell if your thermostat is broken or not.

Steps on how to know if your home thermostat is damaged

  1. Go to the main fuse box in the house and turn off the power to the heating and cooling system.
  2. Remove the thermostat cover holding it and pull it out of the wall. Some thermostats have a lower door that simply rises up or down.
  3. Locate the red and white wires that are attached to two screws on the front of the thermostat.
  4. Insert the screwdriver into the screws and turn them to the left until the ends of the cables come loose.
  5. Wrap the ends of the two wires two or three times.
  6. Return to the main fuse box and turn on the power again for the heating and cooling system.
  7. Go to the heating or air conditioning and verify that the two turn on.
  8. Then, feel the air coming out of the vents to see if the temperature is right. If the unit turns on and the temperature is adequate, then the problem is the thermostat and you will have to replace it.

How to tell if your car’s thermostat is damaged

The thermostat is responsible for controlling the coolant inlet to the engine. When the engine starts to raise the temperature, the thermostat closes and prevents the coolant from passing to the engine until it reaches the ideal operating temperature. Then it opens to allow the passage of the refrigerant and level the temperature. Sometimes the thermostat fails and gets stuck. In this case, we present to you the best DIY tricks to discover what the problem could be.

Indicators that may show failures in the cooling system

The level of coolant or antifreeze: This always has to be between the minimum and maximum level. It is not recommended that it is above because it starts to boil and aerate the system, much less below the level

Refrigerant leak: You should check if there are puddles under the car. The coolants are colored (green, orange, red), if there is moisture in the hoses, gaskets, covers or in the lower parts of the engine.

Scents: The coolant has a characteristic sweet, burnt, or sour smell.

The Temperature indicator: The coolant temperature indicator is on the instrument panel. It should always be below half. If it rises, it indicates it has temperature problems.

How can you check a thermostat?

The process is quite simple and anyone can do it at home.

How can you check a thermostat

What you’ll need

  1. A pot
  2. Hot water
  3. Cold water
  4. A thermometer (optional)


  1. Place a container of water in a heater or stove, let it warm until it reaches the boiling temperature.
  2. Place the thermostat with a plier
  3. When the water reaches the boiling point, the thermostat begins to expand, so that the spring moves the plunger, closing the circuit. In this way, we can check if the thermostat works. The boiling temperature can vary depending on the atmospheric pressure. At sea level, it is 100 degrees Celsius. At the peak of Everest, the boiling point of the water is 60 degrees since it is located at 4,810 meters high. The boiling point of the water is different and varies with atmospheric pressure where the test is done.
  4. After the water reaches the boiling point, then we can put the thermostat in a vessel with cold water and see how the thermostat reacts. This way, we can check if the thermostat opens and close. Aided by a thermometer, we can identify the temperature at which the thermostat closes the circuit. Hence, this information can give us a diagnosis regarding the thermostat.


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