Well I can't figure this problem out so hopefully the Guru's here can help me out a little. I needed to change the compressor on my LS engine which was running a 5H Sanden compressor. When I took the A/C line off it damaged the coupling and I had to have the line replaced. It took about 3 weeks to get the new line back. I then installed a 7H Sanden compressor that is the exact same size as the 5H and installed a new drier. Hooked everything back up and put a vacuum on it for 45 min and then let it set for an hour. The vacuum held and all was going well. The A/C is controlled by the Jeep computer still.

Then the problem hit, I started the Jeep, turned the A/C on max, and rolled down my windows. When I got back to the engine bay the clutch on the compressor had engaged (without any freon). I quickly stopped the Jeep and double checked everything. Tried it again and it did the same thing. I searched the web all over to see if anyone else had this problem but could not find anything. All indications were pointing to the Low/High pressure transducer so I bought a new one and installed it. I tried filling the system again but the compressor continues to kick on without a drop of freon in it.

I bought a diagnostic machine and it shows that the transducer says there is no pressure in the system and is reading 0.08v (not enough for anything). If I unplug the transducer then the diagnostic machine shows like 600 psi and 4.89v and turns off the clutch on the compressor. I am at a loss as to where to go next so any recommendation will be helpful. Or if anyone knows exactly how the computers are working to make the A/C work.

 

See attached schematics for my 2016 LT conversion. I think you are describing the pressure sensor in a fail safe mode IE no signal = high pressure so system shuts down. Are you using a manual pressure gauge? If there is no R34 in there it is impossible to have 600PSI in it. Hopefully the drawings may help.

 

Sixty4x4, thank you for the drawings. It confirms to me the only thing monitoring the transducer is the TIPM which is controlling the AC clutch. I think there must be an issue inside the "electronics" portion of the TIPM. You are correct about the fail safe mode shutting down the compressor. My only problem is the low pressure fail safe is not working but the high pressure fail safe is fine. I am using a Autel MK808 diagnostic machine to see all the parameters the computers are seeing. I also have a set of AC gauges on the low and high side ports to see that the vacuum has pulled everything down to near 30 bars.

I think I will dump a can of freon in on the high side with the engine off to make sure there is freon in the system and then start her up and finish everything on the low side. I will just have to hope that sometime later in life it doesn't leak freon and then burn up the compressor. Thanks again for the information.

 

You use the word 'freon' but please ensure you use R134a and compressor lubricating fluid in there. Also I believe it is 20 ounces max fill quantity.