I recently converted an automatic transmission car to a manual (M47) and, at the same time installed an engine with half the miles. The engine and transmission were both from an '87. When completed, the car ran as it should and drove well. However, I noticed that when driving with the A/C on, there was a pronounced loss of power when the compressor cycled on. It has been a long time (15 years or so) since I have driven a 240 with working A/C, but I am assuming that it is normal. The customer is complaining that the loss of power with the A/C on is getting worse. I think it is his imagination. I can't imagine what could cause this. Any ideas?

I looked at the wiring diagram in the Bentley manual and found that there are two inputs to the ECU related to A/C; the A/C microswitch and an input from the compressor. I could not find any details as to what these inputs are used for. I am assuming they are for idle compensation. Am I right? I tested the A/C microswitch while completing the OBD diagnostics upon completing the project.
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1966 122s, 1968 142s, 1969 144s, 1979 245dl, 1989 244gl