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a/C Compressor clutch not engaging
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Author
Posted 5/23/2021 2:37 PM
AGuess
Elite Veteran


Date registered: Apr 2006
Location: Holly Springs NC
Vehicle(s): 93 500GE, 93 500GE, 2002 G500
Posts: 717
500
a/C Compressor clutch not engaging

Hi Everyone,

93 500GE. M117 engine.

WDB 463 228 170 90 348

The A/C compressor clutch is not engaging when I turn on the A/C.
1). All fuses are ok. That the manual identifies as being for the A/C. The blower works.
2). I don't know where the K-7 Relay (I think that is the A/C relay but am not sure) is located or how to test it.
3). I had the system checked for leaks, evacuated, recharged with R134. No leaks.
4). Clutch spins freely

Is there a easy way to check voltage at the top of the compressor and if yes, can you tell me what to check?

There is a two screw connector with lot's of wires to it.

I am trying to not take the center console off the dash to check the switch.

Other things, that I don't know how to check is the pressure sensor, etc.

There is on black/red stripe wire that runs from the top of intake manifold down to the top of the compressor. Any thoughts on what that controls?

I am trying to rule out what I can as I am not sure I can find a local shop to work on it due to age and it being a euro.

Thank you.

Alex.
#242711
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Author
Posted 5/27/2021 9:29 PM
AGuess
Elite Veteran


Date registered: Apr 2006
Location: Holly Springs NC
Vehicle(s): 93 500GE, 93 500GE, 2002 G500
Posts: 717
500
Re: a/C Compressor clutch not engaging

Update
The low pressure switch has continuity.
The aux fans do not come on
I’ve tested all fuses
I can not find the ac relay. Any ideas?
#242716 - in reply to #242711
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Author
Posted 5/28/2021 7:56 PM
AlanMcR
Expert




Date registered: Apr 2006
Location: US, CA, Los Altos
Vehicle(s): G300DT E300DT 230SL
Posts: 3500
2000
Re: a/C Compressor clutch not engaging

Need the wiring diagram?
#242719 - in reply to #242716
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Author
Posted 5/29/2021 5:19 PM
AGuess
Elite Veteran


Date registered: Apr 2006
Location: Holly Springs NC
Vehicle(s): 93 500GE, 93 500GE, 2002 G500
Posts: 717
500
Re: a/C Compressor clutch not engaging

Update.
I pulled all relays inside the dash and reinstalled them.
I cleaned all connectors on the low pressure switch, high pressure switch and the temp switch on the intake manifold. The compressor and the aux fans turned on and ran for awhile and the compressor make noise.

MB classic told me where the relay is and is sending a new one $150, if that does not fix it, I will have to find a shop that works on older 126 MB that have the same AC system. It could be a bad compressor.

I have a wiring diagram, but am not sure it is complete.

Alex
#242722 - in reply to #242711
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Author
Posted 5/29/2021 5:21 PM
AGuess
Elite Veteran


Date registered: Apr 2006
Location: Holly Springs NC
Vehicle(s): 93 500GE, 93 500GE, 2002 G500
Posts: 717
500
Re: a/C Compressor clutch not engaging

Alan, I have a wiring diagram but am not sure it is complete. If u have one that u can email or upload on wetransfer.com, my email address is: AGuessCPA@gmail.com

Thanks Alex
#242723 - in reply to #242722
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Author
Posted 6/19/2021 12:37 PM
AGuess
Elite Veteran


Date registered: Apr 2006
Location: Holly Springs NC
Vehicle(s): 93 500GE, 93 500GE, 2002 G500
Posts: 717
500
Re: a/C Compressor clutch not engaging

It was the AC relay. When I replaced it, the problem is fixed.
Thanks for your help
#242762 - in reply to #242723
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