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Clutch engages for a few seconds then disengages

ron in charleston on Sun June 19, 2011 5:59 PM User is offlineView users profile

Year: 1992
Make: MB
Model: 300TE
Engine Size: 3L
Refrigerant Type: R134a
Ambient Temp: 97
Country of Origin: United States

I had not serviced a/c for a couple of years on vehicle, with 169K miles, which has original compressor.

Since the vent temp was not very low I knew it needed to be recharged, this happens every few years.

So with system evacuated and vacuum drawn down I refilled by weight. It's a converted system so I used only 2.1 lbs. of R134a.

Now the compressor will not come on for more than maybe a second. When it does come on it almost immediately disengages. Then it will do the same thing a little later.

I did not add anymore oil as l did have to do the same thing last year and I added 1 ounce of oil and added dye into the oil. No obviously leak but I can not really see behind clutch. Highly unlikely that evap is leaking as I replaced that a few years ago.

So basically my system was working somewhat and I've done something and it will not work at all.

Any suggestions appreciated.


Evacuated most of refrigerant. Result was clutch will engage but is making a lot of what I think is bearing noise coming from the clutch. When clutch disengages noise stops. Noise also stops when compressor has run a minute or so.

I'm wondering if it is worn out compressor since clutch will not stay engaged when proper weight of refrig is filled or if the noise is just the bearings only and I could just change that bearing if I can find on, actually I recall I could not find bearing and I think I repacked the clutch bearing as best I could some years ago.
Any ideas? I'm thinking I might need to change out compressor.

Edited: Sun June 19, 2011 at 7:10 PM by ron in charleston

TRB on Sun June 19, 2011 11:04 PM User is offlineView users profile

Pressure readings?


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ron in charleston on Mon June 20, 2011 1:16 PM User is offlineView users profile

Originally posted by: TRB
Pressure readings?

I did not even take any. I figured rightly or wrongly that it should work right with a proper charge.

Since I have a spare compressor I'm just going to swap them out. I know the compressor in car now has not cooled well for a few years.

I'll post results after I install spare. Hopefully later this week.

tomw on Tue June 21, 2011 4:08 PM User is offlineView users profile

If the noise stops when the clutch disengages, then the noise is coming from the compressor, which sits still until the clutch engages. I think I would do what you propose and swap compressors. I would drain as much oil as I could from the old one, and measure that amount into the replacement compressor, adding whatever 'smidge' you want to make up for the amount that you didn't want to wait for to drain... Or let the old compressor drain for hours or days until you think you have most of it out, and then add the 'smidge' you think it would take to coat the pistons, cylinder, swash plate and 'sump' of the compressor... Either way, you will be swagging.
I'd bet the compressor is dying.

simplificate and add lightness

ron in charleston on Wed June 22, 2011 5:50 AM User is offlineView users profile

I'd bet the compressor is dying

It's not dying it's dead. I removed old compressor and I turn compressor there was no suction form the side that should be producing suction. Replaced with spare compressor, pulled vacuum and when I check this morning it had leaked down some. I'll put some dye in and charge and see what happens.

ron in charleston on Sun June 26, 2011 3:14 PM User is offlineView users profile

Found two leaks, fixed with new o-rings. Charged 2.028 lbs. of R134a. With outside ambient temp at 97 degrees the vent temp is between 46-47 degrees. This was on the test drive where I drove on the interstate. Stop and go traffic is not that low of vent temp. But it's always been that way since it's a converted system that used to hold 2.4 lbs of R12.

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