Vibrating sound when AC is on. What is it? - PeachParts Mercedes-Benz Forum

Richard Wooldridge · #1 08-16-2007, 02:47 PM

Some likely problems might be (1) an overcharge, causing too high a load on the compressor, or (2) a blocked expansion valve, causing very high pressure and corresponding overload on the compressor. Question: Did the repair tech flush the system and replace the drier? If the old compressor was in the process of failing and/or failed, those things need to have been done to assure a successful repair. Otherwise, the expansion valve would surely get plugged up with contaminants from the old compressor. So, you should make sure that the system was properly serviced! A new compressor should make no noise when properly replaced. Compressors do make an intermittent load on the drive belt, which can cause a loose belt to vibrate, so the belt tensioner is a distinct possibility, as the motor mounts would be if the vibration occurs at idle.

Ocean View · #2 08-16-2007, 03:19 PM

Quote:

Originally Posted by Richard Wooldridge

Question: Did the repair tech flush the system and replace the drier?

If the old compressor was in the process of failing and/or failed, those things need to have been done to assure a successful repair. Otherwise, the expansion valve would surely get plugged up with contaminants from the old compressor. So, you should make sure that the system was properly serviced! A new compressor should make no noise when properly replaced. Compressors do make an intermittent load on the drive belt, which can cause a loose belt to vibrate, so the belt tensioner is a distinct possibility, as the motor mounts would be if the vibration occurs at idle.

Yes, the tech flushed the system and installed a new drier.
The vibration is more noticeable at idle than while driving.

brewtoo · #3 08-16-2007, 06:44 PM

Have a look at the belt tensioner and related parts.