Just put the official Volvo R134a upgrade kit in my 86 245 DL and have a problem charging the system. I evacuate it and it holds between 20 - 30 psi. When I insert the R134a through the low side port, which has been upgraded to use the 13 mm adapter and the push on connector for the manifold's hose and try to put in a can of R134a the system reads 100 lbs. on the low side and zero on the high side. Running the car with the a/c clutch wired through to operate so that the compressor is running does not to reduce the high reading on the low side. The high side reads 0 throughout. I'd really like to believe that my R134a service adapter is the cause of this failure to load the R134 into the system, but then it worked when I sucked down the system with the vacuum pump. Unless of course, as I am beginning to suspect the pump is only reading a negative 20 psi from the manifold's hose to the back of the low side port and the likewise when I go to add Freon it is getting a reading of 100 psi from the same hose? Any body got a means to approach this problem?