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-   -   Re: 1986 300E A/C malfunctioning (http://www.peachparts.com/shopforum/tech-help/3928-re-1986-300e-c-malfunctioning.html)

Nick Jamal 04-27-1999 09:05 PM

Regarding an earlier post where I described the climate control working only intermittently - I have a few more details. It's finally warming up outside and I NEED air conditioning. After replacing practically the entire A/C system last year, I'm still having trouble. When idling, the compressor cycles regularly, and will do so forever. However, when the throttle is applied, the compressor cuts out - and stays off until the car is restarted. If the AC is activated while driving, it operates for a little while and then cuts out - again until the car is restarted. As I said, most components have been replaced, including the compressor, condenser, receiver/dryer, and the pushbutton control unit. When the MB dealer performed the socket box test, the suggestion was that the auxilary water pump (electric) was drawing too much - and interfering with feedback to the control unit. At their recommendation (and my expense), the pump was disconnected. This actually seemed to work for a while - but the problem is back, and I'm sweating. Any help/ advice would be greatly appreciated.

Benzmac 04-27-1999 10:38 PM

I have had alot of experience with this subject and there are only a few things that can cause this.
1. If the poly-belt tensioner is the least bit loose and allows any slip, the compressor will cycle off until restart.
2. If the compressor relay is defective it can cause this. It isn't a pushbutton unit problem if it cycles OK.
3. The sensor in the rear of the compressor can go bad only above a certain RPM. It sould generate an AC sine wave at all RPMs going up in voltage as the RPM's increase.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM



M.B.DOC 04-27-1999 10:47 PM

Mercedes designed the a/c compressor with a cut-out system to protect the multi-rib belt in case of compressor failure! The relay & related parts have costed Mercedes owners $$ & frustration. Sounds like your compressor relay doesn't THINK the the a/c compressor is going the correct speed, most likely a BAD A/C COMPRESSOR!! I understand that some "aftermarket" rebuilders of electronic componets (a/c relay) rebuild the relay & leave out the speed signal imputs.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS M.B. TECH


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