A/C Compressor question - W123 - PeachParts Mercedes-Benz Forum

RML · #1 12-12-2009, 09:37 PM

I was getting caught up with maintenance on my 84 300D today. My son reminded me that I still need to replace the A/C compressor belt that broke last spring. So I loosened the compressor bolts, was trying to slip it on and noticed that the compressor pulley was not spinning at all. It is supposed to spin freely, right? I occurred to me that maybe the compressor froze up and that is why the belt broke.

JEBalles · #2 12-12-2009, 10:57 PM

I have a compressor that I got off of an '81 300SD I don't know if it works, PO said it was "going" but I don't know why he thought that. The hoses were already disconnected and the belt was super loose. It does spin freely. PM me if you want it.

the heap · #3 12-12-2009, 10:58 PM

Yes.

When the A/C is OFF, the compressor clutch is de-energized, and the pulley will rotate freely. When the A/C is ON, the clutch is engaged, and the pulley is connected to the compressor. There will be resistance to rotation. Your compressor might be siezed; with the A/C ON, can you turn the clutch with a wrench?

'77 300D

Cr from Texas · #4 12-12-2009, 11:00 PM

Quote:

Originally Posted by RML

I was getting caught up with maintenance on my 84 300D today. My son reminded me that I still need to replace the A/C compressor belt that broke last spring. So I loosened the compressor bolts, was trying to slip it on and noticed that the compressor pulley was not spinning at all. It is supposed to spin freely, right? I occurred to me that maybe the compressor froze up and that is why the belt broke.

My compressor locked up last year and broke the belt (smoked a lot first).

sixto · #5 12-12-2009, 11:12 PM

The pulley rides on a bearing on the snout of the compressor. Even if the compressor is seized, the pulley should spin freely. You might only need a new pulley bearing. Only because sometimes parts of a compressor cost more than a complete rebuilt compressor.

As the heap says, see if you can turn the compressor by the spring plate ahead of the pulley. I suppose you can try the nut as well on a GM compressor but I'd advise against it on a newer MB with a Nippondenso compressor. Autozone free* rental tool #27000 is a big pin wrench to hold the spring plate while loosening/tightening the nut. You should be able to use the tool to turn the compressor shaft through the spring plate with not much effort. If it feels like the tool will slip or break, the compressor innards are probably toast. *Around here the tool rental policy is you buy the tool and get a full refund when you return it in reasonable shape within 60 days. This particular tool costs ~$25 from the rental tool collection.

Sixto
87 300D

sixto · #6 12-12-2009, 11:20 PM

Here's a what's involved if it's the pulley bearing - http://www.cadillacforums.com/forums/cadillac-tech-tips/123304-c-clutch-pulley-swap.html

Sixto
87 300D

RML · #7 12-12-2009, 11:31 PM

Quote:

Originally Posted by JEBalles

I have a compressor that I got off of an '81 300SD I don't know if it works, PO said it was "going" but I don't know why he thought that. The hoses were already disconnected and the belt was super loose. It does spin freely. PM me if you want it.

Thanks for the offer JE, but if I need to replace the compressor, I would go with a new one, or at least a rebuilt one. There is a lot of labor involved that I do not have the tools or expertise to do, and I would not want to have it done twice. If I am going to have it replaced, I want it to last a long time.

RML · #8 12-12-2009, 11:47 PM

Thanks for all this input. A/C repair is one area of the car that I have not ventured into and do not feel very comfortable with. My 84 needs to go in for state inspection so I am going to leave the belt off and ask my trusted mechanic to take a look at it and tell me what he thinks. I'll mention the idea of it maybe being just the pulley bearing. At least I am going in with some knowledge of what is going on.

If it is the compressor or just the pulley bearing and needs repair, is there any wisdom in having it done now as opposed to waiting until next spring? I am in PA and will not need the A/C until next June of July. I have not actually run it since last spring when the belt broke. I know there is a lubricating oil in there to keep the seals in good shape. Is it deteriorating by not running for so long?

RML · #9 12-12-2009, 11:49 PM

Quote:

Originally Posted by sixto

Here's a what's involved if it's the pulley bearing - http://www.cadillacforums.com/forums/cadillac-tech-tips/123304-c-clutch-pulley-swap.html

Sixto
87 300D

This is a great writeup, Sixto. Thanks for the link.

rscurtis · #10 12-13-2009, 11:15 AM

While you're in there, slide the steel shell off the compressor and see what the inside looks like. If it's good, you can get replacement "O" rings from McMaster-Carr, then replace the shaft seal and the offending bearing. You should then be good for many more years of service. If the inside of the compressor is black and dirty, then quit while you're ahead.

leathermang · #11 12-13-2009, 02:21 PM

You did not tell us if you are running R 12 or what kind of compressor you have on the car... those things could affect the advice people give you.

RML · #12 12-13-2009, 02:45 PM

Quote:

Originally Posted by leathermang

You did not tell us if you are running R 12 or what kind of compressor you have on the car... those things could affect the advice people give you.

I am runnning R-12, but did not write down the name of the compressor. I pulled the file that the PO gave me and see that the compressor was replaced in 2004 along with the reciever/drier. I probably would have switched over to R-134a at that point but the car was in Georgia and maybe the thought was that it would not have cooled as well. I see that the PO paid $725 for a new compressor. Ouch. I see it listed in the AllParts Express section here for $346.

I'll get the name of the compressor and post it. I do remember that it had a yellow label and was manufactured in Ohio. It is pretty dirty under there, with all of the crud I cleaned out from under the front of the car and knocked onto the floor. And I am all nice an clean today.

I was thinking also that it would be nice to pull the compressor out and have a look at it, then put it back in the spring. But I do not have the equipment to recover the R-12. Does anyone think this would be a good idea? I am guessing that I would have to put in a bridge with the proper fillings between the refrigerant intake and output hoses to seal the system while the compressor is out. If the system were drained, I would be willing to tackle taking the thing out an sealing it up. But, when you drain it, don't you have a vacuum until refrigerant is put back in?

Matt L · #13 12-13-2009, 05:59 PM

Vacuuming comes right before charging with refrigerant.

You won't get the compressor out without discharging the system, so you should get it reclaimed first. Don't drive around with open lines; be sure to plug them.

RML · #14 12-14-2009, 12:27 AM

I got to thinking this evening. The pulley looked a bit rusted, and I wonder if the PO had the compressor replaced but they put the old pulley back on and that is what froze up. Would this be a normal way to do the procedure if you were replacing the compressor? When I look at the picture of a new compressor on the AllPartsExpress page it includes a new pulley.

RML · #15 12-14-2009, 10:43 PM

Quote:

Originally Posted by leathermang

You did not tell us if you are running R 12 or what kind of compressor you have on the car... those things could affect the advice people give you.

I got back under the car this evening to take the belt out. The compressor is a Delphi. And as I mentioned earlier, I am running R-12.

I talked with my mechanic on the way home from work. He is willing to evacuate the system for me and pull the compressor, but was not sure if he would be able to find the correct size plugs to seal up the system for the winter. I noticed this evening that the two hoses come into a bracket whereby they are attached to the compressor. From what my mechanic said, if this is the setup, it may make it more difficult to seal off. I'll know after Wednesday when I take it in.