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Benz Mondi · #4 07-09-2015, 12:00 PM

Quote:

Originally Posted by lsmalley

Problem is power not going to clutch, not too little or too much refrigerant. 0v at a/c connector for clutch and 0v at the a/c cutout switch (attached at receiver/drier). As stated before I ran a straight +12v to the compressor from the (+) battery terminal (car was off) and I heard and saw the magnetic clutch engage. I then wired up the relay bypassing everything and can no get the clutch to engage and disengage with the inside cabin switch that also controls my high speed fans. With this bypass set-up my a/c is now fully functional and pressure on hi/low side is good, but I still would like to know why there is no power. I even tried changing the MAS relay and still 0v.

In your description above, you clearly point out a problem with the MAS relay. You direct wired 12V and got the clutch to move, but when you used a relay and "bypassed everything" (I don't have a clue how you were able to do that) you couldn't get 12V again. It seems that your scheme to bypass everything didn't work. You even said you changed the MAS and it didn't work. I would suggest that unless you used a brand new MAS as a replacement (unlikely since new ones run $400+) you may have a bad "used" unit as a tester. They are cheap enough, get another MAS, clear the codes and try again. These a/c systems are sturdy and are pretty straight forward. The only other issue could be a bad climate control unit, also not that expensive to replace.