Could the clutch on the compressor be frozen? That would explain the always-on compressor. You can pull the electrical connector (2 pins) at the compressor, see if the compressor sill runs. If it doesm the clutch is frozen. If it does not, the problem is upstream, something (Klima?) telling the clutch to always be engaged.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
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"Oh lord won't you buy me a Mercedes Benz."
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