Is It the Compressor?

[Tom Evans]

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

I just replaced my R4 compressor with a new (not a rebuilt) Compressorworks 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.