Question about AC compressor/clutch.

[drdave]

Early last spring, with the expert help of Jack, I replaced my AC system following a "Black Death" episode. All went well until this spring when my compressor stopped cooling for the most part.

So I replaced the compressor with a tested used one that I purchased from a fellow member. Did the vacuum and re-charge, and it worked well. But the other day I went for a 100 mile drive. Near the end of my drive my compressor clutch let out a long squeal and then the AC quit.

Now the clutch tries to engage, but it doesn't seem to pull in with too much force, but this is simply a subjective eyeballing.

So I figure the compressor seized up or the clutch is not working well. How can I check if the compressor is seized? You can't really turn it when it's under pressure, can you? Can I put a ratchet on it and turn it with it completely charged? Just trying to see how I can do a good troubleshooting without discharging the system.

 

[rangerj]

Doc,
Have you checked the gap between the clutch faces? If the gap is too large the clutch tends not to want to stay engaged.

Loosen the drive belt and see if the clutch pulley turns freely. Then you can turn over the compressor, clockwise, with a wrench. The test for a compressor is 84 inch pounds of turning torque, but this is for a compressor that is fully dicharged, ie out of the car. See if the turning torque is "excessive".

Let us know what you find out and we'll go from there. rangerj

 

[drdave]

Jack, it's great to hear from you again.

I actually have the air gap really small, almost to the point of dragging. I'm going to increase the gap tomorrow and test the clutch to see if it pulls in with any authority. But I'm sure that either the clutch is bad or the compressor is trashed.

The engine has been running on the warm side with the AC on, leading me to believe that the compressor has been shedding some excess heat. It's been kind of strange. The engine has been running cooler at idle and lower speeds than at highway speed. I know the fan shuts off around 45mph, but it always used to run cooler on the highway.

 

[rangerj]

Doc,

Jumper the low pressure switch with battery voltage and see if the clutch coil become a strong electromagnet. It should become a magnet and draw in the clutch face "with authority".

If the clutch and coil work OK then the next thing is the compresor. Is the compressor causing drag on the engine, and thus causing the heat-up? Is the fan working properly? With the A/C on, or the defrost (which also puts on the A/C), is the fan running? Is the fan running "strong" and at relatively high RPM, or is it sluggish?

The A/C compressor will cause drag on the engine if it is difficult to turn, and this drag is what heats up the engine. You can also get some drag from a clutch pulley with a bad bearing (any of the pulleies on that belt as a matter of fact). Have you checked the pullies, ie tensioner, A/C, and alternator, for free spinning?

Just some thoughts. rangerj

 

[drdave]

Jack, you've taught me very well. There is very little that I don't know about our AC systems. Once you replace almost everything it's committed to memory forever.

I'm going to increase the air gap and apply 12 volts and see if it snaps. I already know that the pulley bearing is not as smooth as I would like and is slated for replacement. Just not real motivated to have to pull the compressor again. The car runs beautifully with the air off, so I thought that the bearing couldn't be causing me too much grief.

The recovery from "Black Death" is not always an easy one! I'll post back later with my findings.

 

[drdave]

Well Jack, the compressor is tanked. I think that I'll just start using my 90. I'm not sure I want to keep throwing money at the 93. To fix the 93 I'd have to replace the O-tube, accumulator, compressor, and the hoses again. It was so much fun the first time, I don't think I want to do it again. And in my understanding, following a "Black Death" episode in our cars the condenser needs to be replaced as well. Flushing the condenser is not enough. As the condenser gets hot, it releases residue that flushing does not get, leading to another "Black Death".

Oh well, the 90's been wanting some attention anyway. As always, thanks for the advice.

 

[rangerj]

Doc,

If the compressor did not disintigrate you may be abel to get away with just replacing the compressor. This is especially true if all your components are not that old or have much use. Can you find another good used compressor?

Just some thoughts. rangerj

 

[drdave]

I purchase the compressors from people on the forum and have them tested at Austin Baker. I may try again, but I think my money is better spent on the 90 now. The 93 is really starting to show its mileage.