Vibrating sound when AC is on. What is it?
 

My Indy installed a new AC Compressor/drier and now it makes a weird rubbing/vibrating sound when the AC is on.
My car has never made this sound before and it feels like the engine is loosing some of its power when it is on.
Could it be that the belt is on too tight?
The sound is not constant and varies depending on the speed of the car/engine.
I noticed it mostly when the car is going about 20-25mph (2,000 rpm)
It also is barely noticeable when the car is idling.
The sound is not noticeable under the hood but only in the car.

I am going to take the car back tomorrow but I wanted to get some ideas as to what it is before I go.

Any ideas?

BTW, the indy used a new OEM compressor.

Possibly overcharged?

Why did you need A/C work? How long was the a/c inop?

Maybe you have a bad motor mount & never realized that.

My AC was not cooling.
The Indy said that the high side was running too high and that the AC was not able to cool as a result.
It has been doing this for the last year.
I had it evac and recharged 2 times which helped only for the first week.
I had the motor mounts checked out about 2 months ago and he said they were fine.

I am very frustrated as I just spend good money on something that seems to have fixed the AC cooling problem but now I have a different problem.

is it the 96 e320? i seem to remember that the left side mount has to come out in order to remove the compressor.i agree that it sounds like a motor mount noise.

Yes, it's for the 96 E320. It has the M104.

If it is the case of the motor mount why does it make the noise only when the AC is engaged?
If I just have the air on, the sound goes away.

I have replaced the A/C compressor on the W210 with M104 without removing the motor mount. In fact, there was plenty of room, so I'm not sure that it is necessary to remove it.

Why would the mechanic replace the compressor for high side running too high? To me that would indicate more of a blockage or TXV problem. If the compressor was shot, it would tend to have trouble creating any type of high pressure.

As for the noise, my E320 also makes a rubbing/vibration noise when the A/C is engaged. That's because the compressor is shot. It still works, but likely has been damaged by very high pressures that caused it to vent refrigerant out of the drier check valve. This is because the PO was driving around with a failed aux fan assembly and shot radiator fan clutch. I have repaired everything but am waiting until this compressor bites the dust before I replace it. Who knows - it may last for quite some time.

My opinion is that either the compressor is faulty (noisy bearings or pistons) or it is possible that the mechanic did not use the correct type or amount of oil.

Thanks for the info. I will bring it up when I see them on Monday.

Very frustrating considering I just dropped a lot of money on this problem.

I talked to the mechanic that installed the compressor over the phone and he said it might be a belt tensioner.
Not sure if that is the case but I just want this thing fixed. :mad:

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.

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

Have a look at the belt tensioner and related parts.

Use a stethoscope on the compressor, tensioner bolt (careful!) and motor mounts. You will quickly find what is making that noise.

motor mounts at idle

i need(ed) motor mounts on two cars... can't tell that you need them except at idle.. did one car... great..

next car will be done by late september.... 1 1/2 hour job

UPDATE:

Indy replaced the Compressor again and it still has the same problem.
He suggested replacing the belt tensioner, still same problem.
He then suggests replacing the valve, still same problem.
Now he suggest replacing hose. I will find out later if this worked.
At this rate, I will have a new AC system. :-(

Doctor suggested heart transplant, still same problem.
Doctor suggested liver transplant, still same problem.
Doctor suggested lungs transplant, still same problem.
Now doctor suggests brain transplant ...
At this rate, there will be a Frankenstein :D :D.

On a serious note, does your Indy do any diagnose at all, instead of replacing the whole system one piece at a time?

Ha ha,
He is new to me but was highly recommended by others.
He diagnosed as above and has had my car for over 1 week.
Highly frustrated at this point.