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1993 400E
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1993 Mercedes 400E with 196,000 miles. Car in near mint condition. A/C acting up and intermittent. Used to kick on if engine turned off and restarted. Now nothing. Bought car new in '93. Car well maintained by one shop over last 20 years. Attempts to fix a/c over last 2 years proven fruitless. Can't believe a/c system and compressor has lasted this long (27 years). Need to fix. Considering new compressor, drier and sensors. Have replaced belt tensioner and auxiliary fan resistors. System seems to be holding 134a refrigerant. Will recheck for leaks. Question is how many sensors should be replaced? Also, could wiring be an issue? Any thoughts would be appreciated.
 

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1993 400E
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Discussion Starter #2
Update to original post - the 1993 400E does not have a KLIMA relay so I assume the compressor and clutch are controlled by the base module. Is this correct and should I replace the base module as well?
 

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W124
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There are a few steps you can take to activate the compressor if it is "tripping" the protection logic. This is a workaround for a failure condition such as high temp, low refrigerant pressure, slow compressor RPM, etc. If it was my 400e I would go for the high temp sensor, receiver/drier, low pressure sensor and compressor and then re-evaluate. It still might not work but if you are intent on getting the A/C working and the system doesn't leak, leaving these 27 year old components to work for much more time would be delusional. They have more than paid for themselves.
 
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