If anyone can help me figure out whether to install a new air conditioning compressor clutch/pulley kit instead of the whole compressor unit, my deep appreciation.

I'll go through what I experienced and my temporary fix using a shorter belt, which bypasses the AC compressor.

2006 W211 E500 4Matic wagon, M113 V8. Noticed that the A/C would lose power during long rides -- output slowed, warmed. If I turned off A/C with the dash button, it blew cold and strong after a few minutes' rest. I thought maybe it was icing up or something.

Couple of weeks later the idle was loud, clattering -- sounded like a tractor/diesel. Soon after, I smelled something acrid/burning. Little white smoke came up from under the hood. Stopped driving, saw that the serpentine belt was smoking around a frozen AC compressor pulley.

I ordered a shorter belt, which is spec'd by Mercedes for the M113 engine to diagnose the AC compressor. (Is was a Continental part number 6K2315, if anyone is interested.) The most difficult part of the install was simply learning the routing pattern of the belt and matching it. Requires a 17mm offset box wrench or socket with short extension.

The pulley wheel was broken. I saw some loose ball bearings. I pulled off the front metal plate -- it just came off easy in my hand without releasing the split ring. The plastic pulley wheel came right off too, along with the outer race of the ball bearing cartridge. I left the inner race on the spindle that goes into the compressor. It looked straight. I opted not to put any force on it and left the remaining part of the cartridge bearing untouched.

The car runs great with the shorter belt. Quiet again. But obviously the AC is disabled.

What causes this type of failure? Is it the clutch in the pulley or something inside the compressor?

If the compressor needs to be swapped, is that something something that's best for a shop to take on, or can a shade tree mechanic deal with the refrigerant?

Many thanks. I'm happy to try to offer more insights if anyone is experiencing the same and wants to install a shorter belt for a temporary fix.

 

The compressor in that vehicle is one of

depending on VIN number.

All the compressors listed above at xSEU1yz variants, i.e. variable displacement compressors without electromagnetic clutch. That is the pulley is always spinning the compressor, and it looks like the one below



Behind the plate on the pulley there is a set of rubber pieces that keep the coupling between the compressor and the pulley. These rubber pieces work as a mechanical fuse, i.e. if the AC compressor seizes, they break and start to burn/smell in an attempt not to burn your serpentine belt. Here is a video showing the internal of the pulley


If you decide to replace your compressor, which is likely busted. Be EXTREMELY careful, you get the correct compressor even if from an MB dealership. You must check if your compressor electronic control valve has or not a diode. How to tell? read the attached document from Denso. In the past, the triangle used to be a yellow dot.

 

Thanks for offering the guide to selecting the right compressor.

Can you or anyone provide more insight on what happens inside the compressor and what happens when it's unbolted from the car? Does refrigerant gas escape?

I understand that the compressor holds some special oil and circulates this oil through some kind of system. And separately, it is circulating and compressing the refrigerant too, correct? This refrigerant is normally a gas at room temperature, correct?

On one web site selling compressors, it recommended diagnosing and cleaning the oil system to make sure it was circulating correctly before a new compressor is installed.

I'm wondering what anyone's experience is with this, or if it's a job that's just better left to a shop.

Thanks again!

 

If the compressor failed because it is just worn but not debris in the system, the system can flushed and the compressor must be prepared with the nominal oil amount (as stated in the picture for that specific model); however, if not flushed there may be some oil along the system and it must be estimated. Usually by properly draining the oil from the old compressor, and substracting from the nominal amount. That is still a wild guess since we do not know if some oil already left the system by other means in its lifetime.

If you can find an honest MB+AC specialist, I will leave it with them if the estimate is reasonable.

 

my 2006 CDI om648 a/c compressor does not have a typical electric clutch as I have worked on lots of other vehicles A/C problems. With My vehicle the compressor is always spinning regardless if the A/C is on or off. There is an electric valve in the compressor that is signaled to open or close, you can‘t physically/visually see if its open or closed.

its probably going to be cheaper to buy a compressor with the clutch installed. check hoses at compressor attachment with a Qtip for metal debris, don‘t use crappy drug store qtips, buy professional ones from Amazon. You will need a vacuum pump made for A/C evacuation, a guage set with 4 ports(hi side,low side, charging port, vacuum port), A/C scale for precisely measuring refrigerant. Probably E sockets and Torq drivers. Air compressor to blow dirt/dust off seal areas and flush hoses. PAG 46 oil with dye, oil injector, UV flashlight. A bidirectional diagnostic tool to access the A/C system. Thermometer with a stem to measure duct air temp. Why did the compressor sieze or was it just a clutch, since the pulley fell off, try to rotate the compressor shaft with pliers.

BUT FIRST Locate the hi side and low side ports, uncap them and depress the schrader for a second to see if the system still has pressure.

Failure reasons: somebody working on it not knowing what their doing, getting air in the system when adding refrigerant, somebody replacing a part and not adding PAG oil in the proper quantity or type. This is not a DIY job if you don‘t have the tools.

in all cases you have to replace the drier part too if you replace the compressor.

 

It does not have a clutch at all. It is a clutchless compressor. You are correct, there is an "electronic control valve" , as described in the attached document above, that controls the amount of compression the "variable displacement compressor" does on the refrigerant. Your should look like the ones below

 

. Hello, I have a question, please. My compressor has seized and the pully is gone rusty and no longer spinning which caused the drive belt to come off. It's a 2004 E 270 cdi. My question is am I able to just replace the compressor and pulley by swapping it over with a used one?or is there more work involved? Thank you

 

Hi

I recently posted a YouTube video showing how to remove the AC Compressor pulley in situ without taking the compressor off the car or disconnecting any lines. Hopefully this might help some people. Mike