The other day we had the a.c. on and noticed that it was not blowing out cool air, shortly after the car overheated. We took it to the shop where he changed the thermostat and a fan. The a.c. still does not work. We tried the a.c. again and once again the car overheated. We have drove the car several times with out the a.c. and it does not overheat. Only when you mess with the a.c. does it overheat. If a fan and thermostat has been changed what is causing the overheating?
My car has an automatic transmission.
The two cooling fans are controlled by a fan controller which is mounted in the center of the engine, above the radiator. The fan controller controls the fan speeds depending on the signals from the engine control module input. A scan of the computer input and output may point to a problem with the fan controller not turning on the fans when the A/C is turned on or the ECM is not turning on the fan controller when the A/C is turned on. You will need to have the system scanned with a device that can test the fan controller and ECM operation. This may take a factory level scanner to properly diagnose the problem. I'd suggest getting some assistance from a certified mechanic who can pinpoint your overheating issue and address your A/C problem as well.
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