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Q: Message on my dash where speedometer is says ac off becasue engie temp is too high

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I got a message today that said my ac is off because engine temp is too high and my temp gauge doesn't seem to be working, it shows all the way cold. When I shut my car off it sounds like the fan or something is still running. I am wondering if this could be my thermostat.

My car has 107000 miles.
My car has an automatic transmission.

A: It sounds as if your car has put itself int...

It sounds as if your car has put itself into a default mode to protect itself form overheating. The fact that the gauge shows it is cold indicates there is likely a problem with the coolant temperature sensor. When this system fails, the PCM (powertrain control module) assumes the car is overheating to protect it from getting too hot and damaging the motor further. The A/C condenser is mounted on the front of the radiator and adds heat to the cooling system, so it is turned off to limit any extra heat sources from contributing to the lack of ability to cool the car sufficiently.

I would begin diagnosing this by connecting a scanner and inspecting the data. Most likely you will see the CTS (coolant temperature sensor) has failed. Keep in mind, wiring to the CTS could be damaged and causing this problem as well. The CTS data should show a temperature that reflects the temperature of the motor. If you have been driving it recently, it will be in the 180F to 200F degree range. If you check the data with the engine cold, the data should reflect the ambient temperature. It is common for a failed sensor to show a reading of -40 degrees Fahrenheit. If you want to have the AC system and related components inspected, a technician from YourMechanic can come to your home or office to diagnose your car and let you know what needs to be repaired.

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