When we try to do a recover on a car, we got a High pressure error message. We try that on different car to be sure the problem wasn't the car. We remove and test every valve on the manifold and check them with a vaccum gauge. They were all ok. I did try to do a recover of only the hose unhooked to the car and i work to pass every step of the recover. Retry on cars and still got this message. Any test i could do to find out if the problem come from the high pressure switch, manifold or any other..... please help

Air Tools & Compressors - Robinair - Cooltech 34788 R134a Automatic Refrigerant Recovery