A/C compressor will not disengage.

[hockeyboysomers]

1983 240d, I have been getting somewhat lower gas milage recently. Last night when the car was idling I could hear a sound comming from the engine.. It is a hard sound to explain, but it sounded like a slow pulsing growl. It's been cool here and I have not needed my A/C for a few days. Today, I didn't have the A/C on but when I opened the hood I could see frost on the large hoses of the a/c system. I looked down at the clutch on the compressor, and noticed it was engaged. I checked the control knobs and they were in the off position. I removed the fuse controling the A/C, the clutch still remained engaged. My question is, is there anything else that can cause the a/c clutch to remain on. If not, can the A/C clutch be replaced without removing the compressor. Any help would be appreciated.

[1980sd]

What type of compressor? My bearing just went out on my R4 and did something similar.

[Yak]

Which fuse, 8 or 12? The compressor gets power to engage the clutch through a relay, that relay gets power from fuse 12, per the schematic for an '81 240D.

It's possible the relay failed in the closed position and is keeping the clutch engaged. You can try pulling one of the relays (ice cube-looking things, DS fender) or the simplest way to release the clutch is to pull the wire off the compressor.

I'd recommend trying to find the relay first since a) that doesn't involve crawling under the car and b) if the problem is the relay, then you don't have a live wire under the car.

[tangofox007]

Originally Posted by hockeyboysomers

My question is, is there anything else that can cause the a/c clutch to remain on.

Your problem could be a mechanical issue with the clutch. Too much of an air gap, the clutch won't engage. Too little and it won't disengage. It's possible that clutch could have had an encounter with a foreign object resulting in dimensional changes. Ruling out an electrical problem first would be the easier troubleshooting option.

[leathermang]

I believe the gap is supposed to be .020 inches to .040 inches ...

[hockeyboysomers]

Thanks for all the advice. I didn't think of the relay. If I'm lucky thats all it will be. I don't remember damaging the unit, but I guess it's possible. If those don't work, I'll check the gap. It's 9:30pm, I'll check tomorrow. Thanks again.

[hockeyboysomers]

YAK, Great advice. It is the fan relay stuck in the closed position. To be sure, I switched the A/C relay with the fan relay and the fan came on immediatly. This forum is a great tool for keeping our old cars running. I check it daily. Thanks again to all who offered advice. Dave