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Old 09-23-2003, 02:29 AM
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Join Date: Mar 2000
Posts: 517
Variable Displacement Compressor Failure - What Happened?

A friend's '98 C230, 44K miles, recently lost the A/C compressor... the unit briefly made a clunking noise when engaged... shortly afterwards, the noise stopped, as did all cooling. The clutch continues to engage when activated and the pulley turns smoothly but the compressor is quiet and high side and low side pressures remain identical.

The local dealer says they've begun to see elevated failure rates for these compressors.

What happened here? M-B offers a reman'ed unit but this is not a cheap unit to replace. Thought the variable displacement compressors were more reliable than the previous generation of NDs.
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Old 09-23-2003, 10:06 AM
MrCjames's Avatar
California Dreaming
Join Date: Jun 2003
Location: SF Bay Area
Posts: 599
One of the problems with R-134 systems is the oil does not blend with the refrigerant. Another issue with the oil being used in the system, it is "Agroscopic" meaning moisture will mix with it thereby effecting the oils ability to reduce friction over time. Another factor could be if your system had a leak prior to this failure, and the oil in the system was not replenished to its proper level.

I suspect the life expectancy of the compressors on the transition systems (1996-1999) will be lower than those of late.

I have been hearing some good things about a synthetic oil called Ice-32. You may want to research it.
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Old 09-23-2003, 12:00 PM
jbaj007's Avatar
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Join Date: Jun 2001
Location: Santa Monica, CA
Posts: 2,053
Hygroscopic means affinity for moisture, although some (even experts) use <hydroscopic>, incorrectly.

Agroscopic = an affinity for farm produce?

Just joking around.

The hygroscopic oils hold moisture that creates some pretty interesting acids that can lead to pinholes in the evaporator (think of the dreaded 140 evap.).

#1 cause of compressor failure according to one article in a MACS? publication is lack of oil.
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
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Old 09-24-2003, 01:11 PM
MrCjames's Avatar
California Dreaming
Join Date: Jun 2003
Location: SF Bay Area
Posts: 599
I knew I forgot to use the correct term thanks for correcting me.

Avoid those farm products when ever possible!!
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