Q: Car makes rattle noise when A/C is turned on, when A/C is off it makes no noise

asked by on July 14, 2017

The car makes a rattle noise when the A/C is on, when the A/C is off it makes no noise, it also makes a squeak when the A/C is on and accelerating

My car has 32000 miles.
My car has an automatic transmission.

It sounds like you may have a damaged AC compressor or compressor clutch. As you may know the AC Clutch is the pulley that spins with the Belt. There are two ports on the rear of the Compressor. One is a Suction Port and the other is the Discharge Port. The Suction port is going to be your larger port and the Discharge port is going to be the smaller port. Refrigerant is sucked into the Suction port, compressed and then it exits out the Discharge Port, then entering the A/C Condenser. Your vehicle’s AC Clutch consists of the Hub, the Pulley, and the coil. The front part of the A/C Clutch is the Hub. Next is the pulley, which is where the belt rides. Finally, under the pulley is the coil, also called a field coil. The Coil is a copper would wire, that functions like a magnetic coil. If the AC Compressor is powered up, electricity engages the coil, and when this happens, it also engages the pulley. The large magnet forces the hub to pull against the pulley. Since the Shaft of the AC Compressor is mated with the A/C Hub, once engaged, it begins to pump refrigerant in the system. Turning whenever the engine is cranked, the A/C Compressor Clutch Pulley will spin even if the AC Compressor is off. If the A/C System is turned on, power is sent to your A/C Compressor Clutch and it will then engage. However, if the pressure in the system (or the refrigerant level) is either too low or high, switches will kill power to the Compressor to keep from damaging it. I would suggest having a professional from YourMechanic come to your location to take a look at your vehicle.

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