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.