This is a repost for another forum but this one seems more active and I wanted to get your thoughts.

Truck has 175k miles on it. The AC stopped working the other day and while investigating I found that the clutch was no longer on the compressor. I put on a spare I had and engaged it. The compressor started spinning very slowly but the clutch was slipping on the pulley. I checked the air gap and it is within spec. When I was tightening the bolt onto the compressor it would spin without too much extra effort so I think the compressor is not locked up. The car has 175k miles so I'm not overly surprised the old clutch came unscrewed but I'm curious why this one won't turn at the appropriate speed.

I let the compressor run for a second with the clutch slipping and it slipped less towards the end. It started to blow out cold air so it seems the compressor is okay. I can turn it easily. Could the coil be pulling hard enough to pull the clutch down but not hard enough to keep it from slipping?

 

If the clutch engages, it will turn the same speed as the pulley. If it isn't turning at the same speed, it isn't fully engaged.

Reduce the clutch gap down to the 'tight' end of the range. If it still slips, replace the clutch with a new one.

 

I'm pretty sure it's around .018-.020, that was the thinnest shim I have. If I take the shim out I don't think there is enough room for the clutch to open. Can I tired coil not pull hard enough? Is there something that would cause a compressor to feel okay turning it by hand but be too hard to turn at RPM?

 

If the clutch is internally shorting it might not be generating the necessary magnetic field to hold the clutch in tight. It's also possible the compressor relay contacts are worn and not supplying full power to the clutch, again resulting in a weak magnetic field.

 

I have an 05 expedition that is doing the same thing. It will turn by hand but slips occasionally sometimes when it cycles on and off. Of course I'm not hand turning it with the engine or ignition on. I can't leave the thing idling anymore because I might come back to it burning the darn clutch up. It does this a lot more with the rear air on I also noticed.

 

I just discovered that the AC lines to the rear leak when I turn it by hand. I imagine its a lot worse when turned by motor. Thoughts?

 

Can I do anything to test for either of these? I'd like to know for sure if one or the other is bad before buying the new parts.

 

Check for voltage at the coil. I'm not sure if you can do this with the key on and the engine off. So to be safe, first remove the connector from the compressor and connect you DVM to it, then go start the engine and turn the A/C on. You should have an absolute minimum of 10 volts, with 13.5+ volts being ideal. If you had less than 10 volts the problem is with the vehicle and not the clutch coil.

After that, turn the engine off and now measure the ohms of the clutch coil where you first pulled the connector out. The ohms should read 2 to 5 ohms. Anything outside of this range is a bad coil.

 

I tested the voltage coming to the compressor and it is around 13.6 so I think I'm good there. When I checked the coil, I was seeing about 8 ohms. But when I hold the positive and negative leads together on the multimeter I get 5 ohms, so I figure if I take out the 5 ohms from the wires I come in at about 3 ohms across the coil.

I ran the used clutch again for awhile hoping it would wear in to its new application but it never stopped slipping. I would run it and see if it either stops slipping or falls off but I'm afraid I might catch the belt on fire when I shut the engine off.

Each component seems to be functioning properly on its own, but then something is not working in the system.

 

Then as much as I always hate to say this...it might be time to bring it to a shop. Tell them everything you did and let them figure it out from there.

 

I went out today and put the gauges on it to check the pressures and all of a sudden everything seems to be functioning properly. The compressor engages/disengages properly and it's not slipping any more. My pressures were dropping down to 20 and then kicking off the compressor and floating around 150 on the high side so I'll add some 134a, run it, and see what happens.

 

Well my success was only temporary. The bearings in the pulley failed yesterday.

New problem:

It was very stuck. I had to use a puller to get the pulley off and in the process the grooved section for the snap ring broke off inside the inner race of the bearing.

1) Can I use a shorter serpentine belt to bypass the ac pulley? I need the car tomorrow.

2) Can I fix just that part that the bearing mounts to or will I have to buy a whole new compressor now?

Thanks

 

Check you local auto parts store for an A/C bypass pulley. They go for about $40 give or take. This pulley kit takes the place of the compressor and you use the same serpentine belt.

 

The only ones it seems I'm able to find are for 99-01. Mine is an 02. And so far I've only been able to find it online, none locally. Does anyone know a part number?

 

If you can get all of the parts of the pulley and bearing off the shaft and the shaft is undamaged, all you need to do is replace the pulley and the clutch hub. Otherwise, you'll need to replace the whole compressor.

Using those bypass pulleys that use the original belt requires the compressor to be removed.