ACC freezes caused by fan clutch?
 

I hae an 82 300D turbo with AC problems. The compressor on the AC was frozen so I purchased a new compressor and dryer and had them put on by a mechanic that is certified in AC repair. Shortly afterwards, the compressor froze (locked up) again, so I took it to the place I purchased the compresor from and had their "expert" put another new unit in. A few months later, the compressor froze again, I took it back for another niew unit (warrenty). I told the AC mechanic I would be embarassed to bring it back again. He said the compressor failure is being caused by the fan clutch that is behind the radiator. According to him, it was not engaging which allowed overheating and caused the AC compressor to lock up. It doesn't make a lot of sense to be, but what do I know?

I searching the MB manual, I found a section that talks about a viscofan coupling that is not a DIY repair. In the forum I read about people that made a DIY repair by addin a type of Toyota oil to the fan.

Can someone tell me why the AC compressor is continuing to lock up so it needs constant replacement? It has been replaced 3 times by supposedly competent AC repair sepcialists, and I am reluctant to use it because I don't want to break it again so soon. BTW, I live in west texas and the temp during the days is 100+. Ay help would be appreciated. Thanks.

Was the system flushed during these compressor changes?

I seriously doubt that a failed or failing fan clutch would cause the AC compressor to seize.

It will cause excessive head pressure, which will shorten the life of the compressor and will eventually lead to failure.

It's the eventually part which gives me pause, and makes me wonder if the system was properly flushed.

Sorry for the late reply; I had to go out for a shoirt time.

Yes, the system was flushed at least two times by separate mechanics. The first aparantly did not do a goood job, so the second flushed it twice. I assume it was done again when the third compressor was installed, I didn't ask.

When I checked the fan, it seemed to be OK, but my kowledge base is quite limited.

Aby idea what else might be the cause of the constant compressor failures?

I forgot to mention, the fan itself is a little wobbly when the engine is off. It seems to move a fraction of an inch when jiggled. I tried to stop the fan when the engine was cold, with a rolled up magazine with no significant effect except a torn up magazine and little pieces of papper all over the tip of the engine. I thought it was snowing in Texas in August. Anaway, it is obvious the fan IS being engaged.

Dose he put any a/c compressor oil??? The only thing that makes a compresser to freeze is no oil in the compresser, just imagine like an engine with no engine oil running everyday,eventually it lock's up... Is this a r12 system???

Your auxillary fan is used to bring down the high side temperature/pressure as it blows directly on your condensor. Your engine fan shouldn't have any effect on this as it blows directly on your radiator for engine cooling. Is the auxillary fan working properly?

Scott

One more thought. Are they using brand new OEM compressors or some rebuilt one? Rebuilt AC compressors can sometimes be a real crapshoot as to what you get. I had three blow up on me before I broke down and spent $500 on an OEM brand new MB compressor. No problems since.

Scott

As for compressor oil, yes. I know it has ben put in because the 2nd AC specialist said the first had not put in enough. The system has been converted and I think it uses the134a now.

As for the auxillary, I am not certain, but I think it is working properly. I have heard it come on in the past. (I have only had the car for less than a year, and really lke it.)

All of the compressors have been new.

The last compressor that broke was at the paint & body shop. The guy said he started the motor to move it from the paint booth, heard a loud squeal, and found the fan belt oon the floor. It has snapped like a string (it was a new belt).

That is very odd. Since you are paying someone else to do this work and I'm sure you don't want to void your warranty, just go ahead and have someone replace the fan clutch. What do you have to lose? You certainly don't want to have to pay for a new A/C compressor again. Stranger things have been known to happen. Keep us updated.

Scott

Actually, the compressor is under warrenty beacuse I bought the first one new and don't feel comfortable working with AC systems. The other work was a paint and body shop - retired guy working to supplement social security. He did a very good job but probably not as good as I would have gotten if I had paid a regular shop three of four time the amount. Anyway, I am happy with the job he did and the price he charged. Most other mechanical stufff I am trying to do myself (with assistance and tools from the auto-hobby shop on base).

Well, its not the fan clutch that s the issue, the AC work is the problem. You should have stuck with R12. Best thing now is to convert back, replace the compressor under warranty if its warrantable, and flush completely, and install a new dryer and expansion valve. It is recommended that they remove the expansion valve to perform a proper flush form the upper side. If they want to keep the old compressor for some reason it should be removed from the car to flush properly and drain the old oil and its a crapshoot whether the thing is damaged or not so thats why I recommend having it replaced again because the symptoms are you have a mix of R12 and R134A in the oil and thats a bad combination.