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Q: Do I have a bad coolant temperature switch?

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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.

A: In order to verify that the coolant sensor’...

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.

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