I've recently has my ac stop working and I brought it to the shop that replaced my compressor 13 months ago. They had it for about 4 hours with no fix. They said the refrigerant level was fine and think it may be voltage related and to bring it in again another day and the compressor is out of warranty after 12 months. The compressor started to make a loud squeal. I'll likely send it to a different shop if they don't help out on the fix. They said the alternator was only sending out 12 amps.
My voltage at my battery consistently runs at 13.6. Drops to 13.4 when my electric fan kicks in. At the alternator, my voltage shows 14.6 at the main connection. I followed the wire and it gets bundled into a larger loom and then back out of the loom to the battery. Does that voltage difference sound right? For the ac, I checked the voltage at the compressor connection and it matched my battery 13.6/13.4. Tomorrow I'm going to buy some alligator clips and send a 12 volt signal directly to the compressor to make it lock while the car is running.

 

Amps and volts are not the same thing. Basically, what they are telling you is the alternator is getting weak.

 

Jump the low pressure switch to make the compressor come on.

 

My clamp meter cant measure dc amp draw so I can only test the voltage. I'm not convinced yet my alternator has a problem. The shop didn't say the alternator was bad. The compressor does come on and it does cool. It just squeals super loud. It's not from the belt and isolated to the compressor clutch area itself. I don't want to just replace random parts. Saw some other testing methods I saw on youtube. I know all my terminals at the battery are good. Double checked them, cleaned them up better just because and same problem. I will check the back of the alternator connections next at least to isolate the problem any other insite would be appreciated.

 

These vans use a mechanical clutch, what is the vehicle?

 

I did a flexalite electric fan conversion back in April and removed the clutch fan. I also have solar that charges the starting batteries. This is a 2001 ram van 3500 that has an rv conversion. The solar has been installed for about 3 years. It also has the heavy duty alternator 136 amp alternator.

 

Your 136 amp alternator is only putting out 12 amps, and you don't see that as a problem? Your electric fan likely draws 30 amps all by itself when it starts up. 20 or so while running. Add in the a/c clutch, which is a similar load, and what do you expect to happen?

Take the alternator in and have it load tested. May be the voltage regulator...... may be the alternator.

 

yeah that makes sense. The shop had it for 4 hours so would assume they could have figured out it the alt or voltage regulator is bad. The 12 amp output was what the guy told me. I cant verify that. Not sure why they need more time to figure it out besides racking up more shop hours. Yesterday I tested the Ac all loads off including the electric fan. I had 13.6 volts at the harness at the compressor and the same problem. I plan on running a couple of other tests on the alternator before I bring it into a shop again. Alternator seems to be cheaper fix than a new compressor so I'm hoping for that.

 

Ok a little update. I tested the alternator voltage to the battery following some youtube videos and I really got some odd numbers that don't follow the videos. I removed the alternator and the harness on the back has 1 main cable, and a snap on connection with 2 small cables. 1st picture. Not sure if this means the regulator is inside the alternator or if the 2 small wires go to a regulator. I couldn't trace the path. For the large wire, I followed as far as I could reach heading towards the battery but at the end it turned up and I couldn't reach any more. My guess is it goes to this isolated 2nd picture. This is an rv conversion so the isolator makes sense to charge the house batteries. I tested the isolator with engine running and the center post seems to be the same voltage as the alternator. The right post cable seems to go the the battery, and I get about 13.6 volts when the middle post from the alternator shows 14.6.

I think this isolator is the problem. Seems it's not a dodge related item but more of the rv conversion problem. I don't know much about the isolator but I'm assuming it should send out the same voltage as the alternator.

 

If your compressor is squealing when it's engaged how is that voltage related? Either the compressor has an issue or the clutch is bad/worn. Might see if you can turn the compressor by hand it may be seized up. If the alternator is internally regulated it wouldn't have field wires. The isolator just divides power from the alternator and supplies it to the battery who needs it.