I'm not sure why it would be voltage related. That is just what the repair shop told me. All I can guess is that if the voltage/amperage at compressor is too low, the clutch is not engaging all the way? The clutch is not seized and can be turned. I can engage the clutch by sending a 12 volt signal to it. I rigged up a pretty crappy set up to test it. I could only do it with the car off so I couldn't tell if the compressor will squeal. I will have to try a better set up.

As for the isolator, I get that it splits it up but not sure why it would be 1 volt lower than the alternator at the terminal that goes to the battery. That's quite a bit for a 12 volt system with short wires. I'm checking for some specs on that isolator.

I appreciate the input so far and am all over the place on what it could be. Hope it's not a bunch of items.

 

You lose 1/2 a volt across the isolator, that's normal. All of your volt reading sound normal but have you checked for voltage at the compressor both with the AC on and off? If so what were those readings?

 

I only tested the compressor voltage at the harness unplugged with ac mode on. It followed exactly the same as the voltage at the battery. 13.6 with engine running and no electric fan. When I engage electric fan it drops to 13.4. Is there a way to test the voltage with the compressor connected? I see some wires on top of the compressor with some clear connectors so not sure if those can be removed and tested. See picture.

 

If you're getting 13.4-13.6 volts at the compressor then your alternator is fine and the issue is with the compressor clutch.

 

yep I'm coming to that conclusion as well. I think the shop was giving me the run around. I did some more tests tonight and disconnected the compressor harness and started the car with ac mode on. I connected the compressor terminals with direct DC voltage from the battery and got the loud squeal, tried DC voltage from the alternator terminal and got the squeel, and finally I gave it direct voltage from my house batteries which were 100% charged and still got the squeel. I just didn't know enough about how the compressor worked and went by what the shop told me. The shop owner told me specifically that the compressor wasn't getting enough voltage and they fed power to it directly and it worked fine. Guess the guy likes to lie. I will have to bring it into another shop and get a new compressor. Thanks for the input.

 

Does the compressor turn relatively easily? If so, just replace the clutch.

 

I think I would upgrade the alternator if added the electric fan setup.

 

The squeal is because the belt is slipping, which would also explain a voltage drop when the compressor was on since the alternator would slow down. If the compressor turns and isn't locked up then your whole issue could just be a slipping belt. That could be due to the belt being worn or the tensioner not keeping it tight enough.

 

The belt tensioner has 2 stops on it. One is on the non-moveable half and the other is on the moveable half. If these 2 stops are touching each other with the belt installed then the belt has to be replaced.

 

I'll have to check the tensioner again and pay attention to detail. It works smootgly. I've removed the belt and replaced the belt several times, the belt is about 6 months old. You would think this shop would have caught this. The squeel is a God awful loud squak. Not a typical belt squeel. When the clutch first engages, it runs fine for a out 10-20 seconds. Then the outrageously loud squak happens. I'll double check how the belt is doing. I still have my old belt as backup so I can double check with that as well.