Skip the auto shop - Our mechanics make house calls

Q: Do I have a bad coolant temperature switch?

asked by on

My temperature gauge is reading hot almost immediately after I start to run the car. The coolant is full, and I just replaced the thermastat. Is there anything else that my be causing the problem?

My car has 138000 miles.
My car has an automatic transmission.

In order to verify that the coolant sensor’s output reading is correct, you will need to have the engine computer system scanned and look at the data before the engine is even started. The temperature of the coolant sensor and the ambient temperature sensor should be the same or very close to each other.

If the coolant temperature sensor is not reading very close to ambient temperature within a few degrees, then replace the sensor. Make sure all air is bled out of the cooling system and recheck the temperature as it warms up to make sure temperature reads normal.

I recommend having a certified mechanic, such as one from YourMechanic, inspect the car and determine why the temperature gauge is reading hot.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Rattling while accelerating

Hi. This issue can be one of many things. From detonation occurring in your engine, a timing belt needing to be replaced, a faulted catalytic converter, or an issue with fuel that is in your vehicle. More information about when...

Q: my car cranks but won't turnover

By your list, you have replaced parts relating to both fuel and spark. If you're still not getting fuel and spark, then there may be an electronic failure elsewhere in the system. It could be the ECU (Engine Control Unit),...

Q: Radiator cooling fan is not functioning on low power

The resistance reading you tested sounds like it's in range. Most likely the coolant temperature sensor/switch, which controls the fan (on the radiator side tank), has failed and isn't connecting power to the fan when the temperature reaches the design...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...