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2012 E350 CGI Avant Garde Sport, 2011 E350 Avant Garde Cabriolet
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Discussion Starter #1
Everybody tells me that the reason that the A/C compressor is kicking off on my '93 500SEL is the tension is not tight enough causing slipping. The belt and the tensioner were just replaced (again) and it still kicks off. STP belt dressing gives it enough grip to keep the thing working.

Can the tensioner be adjusted to be tighter or is it preset? If it can be adjusted, how?
 

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1997 S600 (sold)
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Maybe it's the clutch that is slipping. Perhaps the clutch needs to be replaced. Or perhaps the AC compressor is resisting turning too much because of internal issues. Maybe it would just be better to replace the whole AC compressor.

Brett
 

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Current 1992 - 500SEL, W124 - 1989 230E (sold)
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DaimlerChrysler said:
Everybody tells me that the reason that the A/C compressor is kicking off on my '93 500SEL is the tension is not tight enough causing slipping. The belt and the tensioner were just replaced (again) and it still kicks off. STP belt dressing gives it enough grip to keep the thing working.

Can the tensioner be adjusted to be tighter or is it preset? If it can be adjusted, how?
Loosen the big bolt in front of the tensioner, then loosen the long bolt thats sticking out of the top of the tensioner until the belt is realy slack, then reset that white pointer marker(all the way to the first mark to your left if standing towards front of your car) and then tighten the long bolt until belt is tight enough and the marker shows somewhere in the middle or to the right side of the scale(again this is bit of a grey area as it depens on how tight you want it and how new the belt is)
and when you are happy with tightness just tighten the front bolt.....iam not certain about how tight these bolts need to be, just dont over do it so you dont cause any damage. Viola and you are all done...may be 10 minutes max. ohh and BTW dont over tighten the belt too much as that will in long term wear out your water pump,Compressor, and al the bearings in all the pulleys....i think its tight enough when you can twist the belt 90 degrees between those top pulleys...
 

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92 500SEL to 01 E320T current 2014 lexus LS460
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I know the 92 is there is a nut on a threaded shaft, and a pointer on the tensioner, push on the belt to see if there is tension. Mine failed and Roadside tried to adjust I would not be hasty on replacing compressor, I do respect Brett, they deleted the safety, and have a updated tensioner for the 95 I think.
 

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1986 560SEL, 1986 560SEL, 1992 500SEL, 1999 S500
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These cars have a speed sensor on the compressor. The computer monitors it and compares it with the engine rpm so if belt slippage is detected the clutch will be dissengaged to protect the compressor. I believe there are low pressure and high pressure switches which monitor the refrigerant pressure. If either one is not satisfied the power will be shut off to the electric clutch on the compressor. This will protect it from running dry if there is a leak or if it is dead-headed from a blockage. The tensioner could be lose as mentioned in the earlier posts. Be careful not to over tighten it as there is no coil spring in it like most tensioners. The center bolt goes through an aluminum sleeve which is bonded to the inside of a rubber donut which is bonded to the inside of the pulley arm. Overtightening can shear the bonded rubber from either surface, especially on an older tensioner--I know from experience!
 

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1997 S600 (sold)
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chuckindetroit said:
These cars have a speed sensor on the compressor. The computer monitors it and compares it with the engine rpm so if belt slippage is detected the clutch will be dissengaged to protect the compressor.
So if it monitors compressor shaft speed, it could be that the clutch itself is slipping (not necessarily the belt). Am I thinking right here?

Brett
 

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1986 560SEL, 1986 560SEL, 1992 500SEL, 1999 S500
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I would say the direction of your thinking is entirely feasible! I once had the opposite happen where a very small piece of rock lodged itself in between the clutch plates and the compressor was always engaged. If you look at the setup there is the standard wiring to the clutch area but then you will find a second cable on the compressor. This is to the speed feedback sensor.
 
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