Hello:

This is my first time posting to this list. Here's the problem.

Car: 1992 400SE 103K by the book 100% complete MB maint.

When the climate control is on there is a very noticable droning/humming sound at exactly 1100 rpm. It happens at idle, and most noticably on deceleration. I have isolated the noise in many tests to only occuring when the CC system is activated. I was told by the service advisor that the compressor could not be bad [as I suspect] as it was activated by a magnetic clutch that is activated by temp sensors in the car. So, If the car was cold inside and you turned the dials both to "High" the compressor should not be on as the temp being asked for by the control unit would be far below the temp inside the car, but, the drone is still present.

I have have had the serpantine belt and tensioners replaced by the dealer which of course did nothing. I then had the frame rail bushings that somehow buffers contact with the cc system replaced by the dealer. The said the problem was a resonance on the frame because of a worn bushing
but again, that has done nothing.

The car was Starmarked [which of course has run out]when the problem was first reported and If I can get an accurate diagnosis, I'm going to try and make them pay for the fix. Any information would be very helpful.

TIA

There was a modification to the A/C compressor clutch for this exact problem! The replacement clutch has 3 large weights on it to stop this noise!! GOOD Luck!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I passed the information on to the dealer where the car has been seen 4 times to try and correct. Now they are telling me that the "Senior Tech" has not been able to locate any record of the change in part or part manufacture.Is there any other information, like a service bulliten on this problem I can give them that would help expedite this fix. Any help would be greatly appreciated.
TIA, Chris

I do have work instructions as this was internal bulletin! Only dealers received this bulletin. Will fax this to you or to THEM! Leave me a fax number here OR in the PRIVATE message center!!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

You can fax it to me at my office. I'll deliver it to the dealer. Don't want to take a chance on them not being able to find it!! Thank you so much!!

Chris Silva
Fax: 410-633-3761

PS. Not sure how to use private messages.

M B Doc,
Please send it to me as a private message too as I also have this problem.
Thanks