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Q: My AC compressor doesn't work?

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My truck only blows cold air when running in high speed but stops when going slow what could be wrong with it?

My car has 198000 miles.
My car has an automatic transmission.

Hello, thank you for writing in. The symptoms you are experiencing can be caused by a few different things. A few common causes are a dirty condenser, faulty radiator fans, or a system that is low on refrigerant. The AC condenser is the component that is responsible for removing heat from the AC system, essentially acting as a radiator core for the AC system. In much the same way as a cooling system radiator, if the core becomes dirty or covered, and airflow is obstructed, then it may not be able to properly release heat from the AC system when the vehicle is not in motion, which may cause the symptoms you are experiencing. Similar symptoms can also be caused by a bad compressor clutch, or a system that needs to be recharged with refrigerant. I would start by checking the condenser, which will be located at the front of the vehicle in front of the radiator, to see if it may be dirty or perhaps covered with leaves or road debris. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.

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