I am having trouble getting my aftermarket A/C system to take a full charge. It's a 134a system. The low side is at 15 pounds, should be between 30-40. The high side is 250-280, should be 190-200. It's a hybrid aftermarket system. When I did my motor conversion I had to get a new compressor, it's a Sanden rear exit with serpentine pulley. All hoses are new, the driers is new. The evaporator and inside blower and components are from Southern Air and were working fine before the conversion, the condenser is also from the old system. The system is free from leaks and holds 28 inches of vacuum and has been evacuated for over an hour, until closing the low side valve on the gauges causes no change in pitch from the vacuum pump. I am confident there is no air in the system. When charging, we placed a box fan in front of the grill to add air flow across the condenser. We did not add oil to the system per the instructions from Sanden. Some dye was added to help find leaks when it was first put together. The condenser and evaporator did sit open over the winter when I was working on the motor swap. It is blowing cold inside, 36-38 degrees out the vents. But I can tell it is still not right because it makes a definite growling sound and the belt jumps a lot when it compressor is on and periodically the compressor makes a real ratchet sound when run at about 2000 rpm for a period of time. My friend thinks it is the reed valves in the compressor slamming open and shut. I have already replaced the compressor once because of a leaking seal and the first one made all the same sounds. I'm pretty sure these symptoms are caused by the low pressure on the low side, but it won't take any more 134a.

Any ideas why? and suggestions of what to try?

thanks

Pat