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  #1  
Old 08-09-2006, 05:36 PM
LarryBible
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Compressor Rotation Sensor

In my quest for getting to the bottom of my compressor dropping out, assumedly due to the rotation sensor, I was told by an experienced MB Tech that sometimes the compressors where such that the shaft thrusts away from the rear sensor causing the sensor to become too far away from the shaft to sense properly.

Mine is tripping out more and more often.

Does anyone know how to adjust the clutch air gap?

Has anyone ever heard of such a thing with the sensor on a worn compressor.

Has anyone ever successfully cheated the sensor circuit.

Thanks for your help.

BTW, the system is indeed properly charged, the belt is good with a properly adjusted tensioner in good condition and the clutch has been recently cleaned to no avail.
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  #2  
Old 08-09-2006, 05:57 PM
david s poole
 
Join Date: Mar 2005
Location: dallas
Posts: 1,822
compressor

larry,i've seen speed sensors go bad and i've seen compressor shafts worn so that they are too far away from the s/s to create enough voltage to hold in the klima relay.then there is the possibility that the klima relay is at fault.i suggest that you jump the klima relay from term 15 to term 87[next to each other] and run car to see if compressor clutch is faulty.[could be a tiny break in magnet wiring that is dropping clutch] this provides the safety on shutting power down to clutch with key off.if this test successful then we can move forward to isolate the problem. david poole european performance dallas tx.
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  #3  
Old 08-10-2006, 08:06 AM
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Larry, easy system to defeat..not really needed at all & MB finally realized that they were not needed..No MB after 1995 uses that crazy system.

Send me a PM & will send you the info on by-pass.
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  #4  
Old 08-10-2006, 08:40 AM
LarryBible
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Thanks guys,

So do I defeat the system by shorting those two pins on the Klima relay? If so will that still give me proper clutch control?

On the 88 300E is the Klima relay in the battery box or in the box behind the fuses?

Thanks a bunch for your help guys.
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  #5  
Old 08-10-2006, 10:11 AM
david s poole
 
Join Date: Mar 2005
Location: dallas
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speed sensor

larry,its located behind the battery.david poole dallas tx.
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  #6  
Old 08-10-2006, 10:34 AM
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Location: NJ
Posts: 49
Hi Larry

I just repaired a similar problem on my 190e. My compressor was kicking off so I decided to remove the clutch to clean it up. When I tried to remove it I held the outer part with a large pair of channel locks while trying to undo the 12mm center bolt. I couldn't get the bolt loose since it just kept turning. On closer inspection I discovered that the clutch had failed. There are two pieces of metal held together by a rubber ring that make up the removable portion of the clutch. This rubber acts as a shock absorber when the compressor engages. This rubber had failed which allowed the inner and outer pieces of metal to spin independant of one another. When turned bt hand everything was OK, but under load there was slippage which caused the compressor to disengage. I had an old clutch laying around from my dad's 300e and replaced just the outer part. Everything works fine now. In order to remove the bad clutch I had to pry the two pieces of metal apart, get the rubber ring out, then hold the inner metal part with a channel lock plier. I did all this with the compressor in place so I wouldn't loose the r-12 and have to recharge. It would be much easier with the compressor out of the car.

Pete
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  #7  
Old 08-10-2006, 11:50 AM
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Location: Plano, TX
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Hi Larry -

Klima relay is easy to locate; it's adjacent to the OVP and helpfully has the word 'Klima' stamped on it.

I actually posted the wiring diagram to use a standard 'ice cube' relay to replace the Klima. Let me go see if I can find the thread...

[Sounds of rummaging in closet...]

Here's one which is helpful, but not the one I was thinking of: Klima relay pin outs (87 SDL or any late 126)

OK, here it is: Klima > Ice Cube - Not Working

Note that because your car is a gasser rather than a diesel the wiring of the ice cube relay is slightly different - the PBU sends +12v rather than ground to signal compressor activation. Concept is basically the same, though.

Lack of kickdown shouldn't be much of an issue on your 5-speed car.

Good luck,

- JimY
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  #8  
Old 11-12-2007, 06:30 PM
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Hi all! I have a 1989 W124 200E here in Manila, Philippines. I had to replace my compressor with a similar 15C Denso unit except that this replacement does not have the compressor speed sensor at the rear (obviously it is not for a Mercedes but for a Toyota or something).

My problem now is that the compressor won't engage and from what I gather from the research I've done in this forum, the likely culprit is this missing compressor speed signal.

As Larry had asked when he started this thread, has anyone successfully cheated this system?

Thanks,
Philip
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  #9  
Old 11-13-2007, 08:00 AM
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You already saw that it is easy to defeat that system.. Send me an e-mail.
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190E 2.3 16V ITS SCCA race car (sold)
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  #10  
Old 06-12-2009, 03:27 PM
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Sorry for reviving this old thread, but,
Is there a way to defeat the rear speed sensor on cars that do not have a Klima relay?

Thanks
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  #11  
Old 06-15-2009, 08:26 AM
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Anyone?
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  #12  
Old 06-15-2009, 10:09 AM
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Quote:
Originally Posted by M.B.DOC View Post
Larry, easy system to defeat..not really needed at all & MB finally realized that they were not needed..No MB after 1995 uses that crazy system.

Send me a PM & will send you the info on by-pass.
I'm having this same problem on an 89 300se. The AC works fine, except that the compressor clutch will sometimes disengage. If I turn the car off and restart it the compressor will come back on and work normally. Just turning off the CCU does not have the same effect. The key has to be turned to the off position for the clutch to re-engage.

Do I understand correctly that the permanent way to defect the system is to jumper pins 15 and 87 on the Klima relay, then reinstall it? What the best thing to use to efect the jumpering?
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  #13  
Old 06-15-2009, 10:33 AM
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For a quick answer try a NEW thread.

No, do not jump those 2 wires OR the compressor will run all of the time. It will burn up!

Send me a PM or e-mail with a valid e-address & I will send info on defeating that speed sensor system.
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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
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  #14  
Old 06-15-2009, 11:13 AM
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Quote:
Originally Posted by M.B.DOC View Post
For a quick answer try a NEW thread.

No, do not jump those 2 wires OR the compressor will run all of the time. It will burn up!

Send me a PM or e-mail with a valid e-address & I will send info on defeating that speed sensor system.
PM sent. Thanks.
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  #15  
Old 06-15-2009, 01:27 PM
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PM sent.

Thanks in advance.

PESuazo
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