Q: A/C blows cold cold when driving but hot when idle an drains battery

asked by on July 08, 2017

So my A/C Blows cold air when driving and warm at idle. But recently i took it for a 5 minute drive and it was ok. But it's when i go to school @130 PM (15min drive to school) and note it's around 90-100 Degrees. So i'd prefer the a/c rather than having the windows down lol. So i went out an checked the belt WITH the A/C running an all of the Pullys are spinning fine including the A/C BUT ONE. i looked on the diagram an it's the Altinator one not spinning and that were i get in to where i start my car it's boggs as if it doesn't have enough juice. but yet it'll still start. So when i have my a/c on when driving my radio cuts out an every other light dims out. On top of the semi cold air blowing WHILE i drive LOL.

My car has 170000 miles.
My car has an automatic transmission.

It sounds like you may have a damaged AC compressor clutch that may be causing a drag on the alternator, resulting in the dimming of the lights due to the alternator not properly charging the battery. 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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