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#1
11-27-2002, 02:26 AM
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Curley 87 300e Air Conditioning Problem
This problem that i have has been discused before, but mine is different as it seems to be temperture related.
The problem is that the compessor cycles properly if the ambient temperture is below 25c. If above 25c the compressor will lock lock out after cycling for the first time, the only way to get it going again is to turn the ignition off then back on again. It will also stay on permently if the fan speed is at full speed, and is nice and cold. I know that it`s been said to look at the belt tension and the speed sensor, these seem to be working correctly, and how could these be affected by the ambient temp. The system works perfectly if the air temp stays below 25c. Thanks to anyone who has the answer for me to fix this problem. 
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#2
11-27-2002, 07:56 AM
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The A/C system pressure will rise when the ambient temp is high. That can cause the compressor to draw pressure from the belt & if any slippage happens then the compressor cuts OFF & stays off until you cycle the key.
__________________
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
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#3
11-27-2002, 03:02 PM
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Not doubting your expertise MB DOC, but why then does the system work when the blower fan is on high, even on 30-35c days, surely the belt would slip then too.
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#4
11-27-2002, 05:21 PM
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The ONLY reason that the A/C compressor cuts off & won't come back on unless you cycle the key is; IF the klima relay doesn't receive the CORRECT compressor speed VS engine speed.
__________________
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
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#5
11-27-2002, 05:47 PM
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Blower speed can definately have an effect on this. High blower speed will cause evaporator temperature to be higher than lower blower speeds. This means that on high speed blower there is a lesser pressure difference between high and low side thus less strain on the compressor.
You have one of a few problems. 1. Belt slipping (belt too loose or compressor siezing under full load) 2. Bad RPM sensor in compressor. 3. Bad klima relay. 4. Faulty wiring from rpm sensor to klima relay. MB doc is exactly correct and you are correct not to doubt his expertise. Brian
__________________
Mercedes Benz Master Tech ASE Master Technician Diagnostic Technician Owner of "Behind the Star Inc." Raleigh NC. www.behindthestar.com brian@behindthestar.com
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#6
11-27-2002, 11:30 PM
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Problem fixed, the evaporator behind the dash was clogged with dust and grime, my local Merc guy said he steam cleaned it, cost me $100aus and all is now perfect, even at the lowest fan settings.
Thanks for all your help guys.
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