Q: Car idles rough with AC on - 2008 dodge avenger

asked by on May 03, 2017

If I am sitting in a parking lot in park or in neutral, I can turn on my AC no problem and enjoy some cool air, but the second I put it in gear (reverse or drive) it vibrates pretty bad whilst idling, however if i'm driving at a reasonable speed my car runs fine until I reach a red light and the engine is at idle again. Runs great without the AC on at all, and on a side note I tried driving with the AC on driving down the highway and after about 10 miles my check engine light came on, and I shut the AC off. The next day I got in my car and the check engine light was gone, I repeated that two more times (the heat and curiosity made me) and the exact same thing.

My car has 100000 miles.
My car has an automatic transmission.

Hello, thank you for writing in. There can be multiple problems with the vehicle causing your issues. First, we need to take a look at the drive belt which sends power to the AC system from the engine. When the engine is running at idle, the lower speed means less power going to the AC. As it stands now, the engine can not handle powering the wheels, and all the other components driven by the drive belt (alternator, water pump, air conditioning) at the same time. This may be due a slipping drive belt (failed belt tensioner, stretched out belt), a component drawing too much power from the engine, or other similar issues with the drive belt. Since the engine runs fine without the AC running, your engine is likely working fine. You should focus on the AC compressor (connected to the drive belt), the tension of the drive belt, and the condition of the other pulleys connected to the drive belt. For more help with diagnostics, contact our service department to schedule an appointment.

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