So is my AC clutch worn out?

[Michael]

I finally got around to looking at my AC system today. A few weeks ago I noticed the cycling was faster than it should be so I immediately thought a bit of Freon had escaped over the winter. It was a bit low, not much, maybe half a can if that much. When I was waiting for the clutch to stop to take my readings, I noticed when it turned back on it would move slowly at first before coming up to speed. It would take about a second or 2 to "fully engage". With Freon pressures right on the money, I was not getting the cooling I would like. I have not looked further into it by going through the flowchart in the manual, as soon as I saw the clutch slowly spooling up to speed I suspected it as faulty. The compressor seems fine and is not making any noise with the clutch engaged. The clutch also moves freely when not on, so I do not suspect the compressor itself.

[DMCMW Dave]

Sounds like it's slipping the clutch. I'd try applying 12V right at the compressor to make sure it isn't a low voltage problem, but typically it would need a clutch. We only sell whole compressors but if you can find the clutch alone, it can be replaced without dumping the system (with some appropriate tools).

The DMC Manual has a lot of info on this, including adjustment procedures.

[David T]

Sounds like it's slipping the clutch. I'd try applying 12V right at the compressor to make sure it isn't a low voltage problem, but typically it would need a clutch. We only sell whole compressors but if you can find the clutch alone, it can be replaced without dumping the system (with some appropriate tools).

The DMC Manual has a lot of info on this, including adjustment procedures.

If the system is overfilled and the head pressures are very high (or a fan motor isn't working or the condenser coil is plugged up) it can cause the clutch to slip, especially after it it has been running for a while and it is very hot. Another cause is if the gap is not set properly when disengaged. That can be adjusted, refer to the Workshop Manual N:10:09. It is also possible you ran low on refrigerant oil and the compressor is worn out. Happens when you have a lot of leaks and are constantly refilling with freon but never checking and replacing the lost oil. See Shaft Turning Smoothness Test N:10:04 and Oil Check Procedures N:10:03. The Sunden site has instructions on how to make a dipstick. Use the 0 angle position and the 510 takes 2-4 oz. Last, if the system is contaminated the compressor may be bad or the orifice tube is plugged up and running your head pressures way up.
David Teitelbaum

[Michael]

Thanks for the help and advice. I didn't drive it when I checked and charged it, but I did drive it to the track to go running around 5pm and the AC was working pretty darn well. I think I just got the condenser heat soaked from sitting in the garage idling for 30 minutes while I charged it.

Although the compressor was cycling correctly and the pressures looked good, the clutch was still taking a second or so to come up to speed so I will check the gap and if that's not it I will probably just keep an eye on it and maybe replace the compressor assembly later this year or early next....or as soon as I can find a nice AC machine for cheap. I don't have a recovery system yet, I can pull it down and charge it, but I cant recover my Freon, and freeze 12 on ebay is darn near as expensive as R-12 was in the day. (One of my dealerships I work got me some for 20 bucks a can so I am going to buy about 6-8cans to keep in storage while I can.)

Anyway, she is working fine for now.