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Is it the Compressor?

SMAir on Sun April 26, 2009 4:23 PM User is offline

Year: 1981
Make: Mercedes
Model: 300SD
Engine Size: 3.0L
Refrigerant Type: R12
Ambient Temp: 79degF
Pressure Low: 60
Pressure High: 125
Country of Origin: United States

I just replaced my R4 compressor with a new (not a rebuilt) compressor, along with the receiver-dryer. I have thoroughly flushed the entire system twice. I also carefully added oil throughout the entire system, including 90 Ml in the compressor. I turned the compressor over by hand for 40 revolutions. The system held a good vacuum overnight. Total evacuation time was 4 hours.

When I started adding R12, I noticed that the low side was not going down as I would have expected and the high side did go up as high as expected. There was some cooling, about 5 degrees differential from ambient. One other thing I noticed was that both needles on my gauges were fluttering, something I haven't noticed before.

Which brings me to the title of this post: Is it a faulty compressor? Did I do anything wrong in the installation? I have installed about 8-10 R4s and this is the first one that acted this way.

Thanks for your help.


SMAir on Mon April 27, 2009 11:26 PM User is offline

I replaced the suspect compressor tonight with a known-good used compressor. That was the problem. As soon as the compressor clutch kicked in, the low pressure went down and the high pressure went up to the expected values. I figure that the suspect compressor had one or more bad reed valves.

Edited: Mon April 27, 2009 at 11:26 PM by SMAir

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