R12?? I did not say R12 anywhere in the post. HC-12a (AKA 12a) is what I would be filling the system with if it were low. If have not added anything to the system as yet.

 

I think he means R134a as that's what he had in the picture anyway. There will be 12V at the compressor clutch if there's a call for cooling and neither the lo or hi pressure cutouts are engaged.

If no R134a has ever been added to the system, then it can't be overcharged. So that leaves either an undercharge or electrical/control problem.

Edit: Oops, didn't see post #21. Why would you put something other than R134a in the system?