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Q: Car overheats when running A/C

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When runing A/C car overheats standing at a stoplight or stuck in traffic for a time.When it has cooled I've checked the fluid in radiator and plastic reservoir and they are fine.

My car has 190000 miles.
My car has an automatic transmission.

A: Your Jeep has a mechanical cooling fan and ...

Your Jeep has a mechanical cooling fan and an electric cooling fan. The electric one is hidden in the fan shroud. Its main purpose is to turn on when the A/C is on. It is a quiet fan, so you may not have noticed when it stopped working. It is powered by a 40 amp fuse in the box next to the battery. The fuse powers the relay, the PCM (engine computer) grounds the relay when it is commanded on. If I were to venture a guess, the fan motor is usually what fails. If the fuse is blown, you can replace it. However, it will likely blow again due to the motor drawing too much current.

What you should do is test the circuit, relay, and motor to find the problem. This would be a good time to test the mechanical fan, too. It is a thermodynamic fan. It has a clutch that freely spins most of the time. When the temperature rises to a preset number, the fan will gradually engage until the temperature is lower. This could be working fine, but the engine needs both fans when the A/C is on. If you would like this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose your overheating issue and make any needed repairs.

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