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  #22  
Old 08-08-2005, 10:14 AM
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Join Date: May 2002
Location: Blue Point, NY
Posts: 25,396
Quote:
Originally Posted by zafarhayatkhan
Looks like you have already ran the 6-7 tests for the Compressor Clutch Relay.

You may want to run the AC Control Unit Diagnostics. alldatadiy lists all the tests.

The compressor engagement on my car was intermitent. Then it would engage at startup but disengage shortly. Bridging pins 5 & 7, the compressor stayed engaged. Repalced the Compressor relay. Did not fix the problem. Took it to the MB dealer, that is another story! I have yet to find a satisfactory MB dealer. End result, I was overcharged and problem not fixed. I declined the $675 speed sensor repair. For that price, one can get a new compressor!

Ran my own checks, all 6 of them for the compressor relay. Ordered the ICe Cube Relay from ebay. Meanwhile, found power connector at compressor loose. Replaced connector, around $5. Everything working fine. Temperature at the vent 38F.

Bridging pins 5 and 7 eliminate the Klima and the PBU from the system. So, you really don't know anything, at that point, other than the compressor clutch works properly. The problem can then be any of the signals to the Klima, the Klima itself, the PBU, or any of the signals to the PBU.

In my case, using pin #10, the ground from the PBU, the problem remained. So, this now effectively rules out the Klima and all inputs to the Klima.

A second PBU eliminated the problem, however, it's more likely that the evap temp sensor is out of limits (2.2K resistance) and causing a default in one of the PBU's. They are not exactly identical........one of them is a newer version and must have slightly different internal circuitry.

I hear you regarding the dealers. You take the vehicle there thinking that they have better knowledge and troubleshooting skills than you do. In reality, you get a parts changer with his head up his ass.
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