I was at my mechanics' shop this afternoon and we were chatting about the A/C system and the oil that is used in the various parts. He was suggesting (my mechanic) that there is a posibility that the previous owner (or another mechanic) may have added an improper oil to the a/c system. The pressures were doing the opposite of what they should have been doing in my system (high when they should have been low, and vice versa).

Would the addition of the wrong type oil in the system cause these rather bizzare anomalies? He had mentioned that the MB a/c oil is a blend of ester(?) oil and something else (something to that affect).

TIA-

Stephen Davis
1988 300E 90k miles
MBCA N. Texas Section


[This message has been edited by CafcoTX (edited 06-19-99).]

Freon requires different types of oils than does R134a. Which system are you asking about? If its R134a than M.B. recommends only there own PAG oil. However since the older cars w/GM compressors require ISO 150 oil & Nippendenso compressors require ISO 46 oil one(1) weight of oil isn't correct. With R134a systems stay with PAG oil as most ester oils will break down under extreme conditions. Use "double end capped" oil, as it can be compatible with small amounts of oil from R12(freon) systems.
Can too much oil(or incorrect type) cause problems; Yes & that is the cause of most a/c compressor failures. Most shops don't have correct information on this subject(dealers incl).

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MERCEDES BENZ MASTER GUILD TECHNICIAN
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My system is R12 which I believe was 'stock' for this year model.

Thanks,

Stephen Davis
1988 300E 91k miles (turned 91k today)
MBCA - N. Texas Section

The only thing that I have seen cause this is a faulty reed valve in the compressor assy.

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Benzmac:
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