hey, im currently working on an airdale heat pump, it is an all in 1 unit that sits on the roof and is ducted, it has 2 compressors which both have been changed and run on r22. the problem is when comp 1 runs the suction goes to 70psi and discharge pressure to about 170psi and the evap starts to ice up nicely. then after 2 minutes of running,if that, the low side starts to pull a vac and the evap melts. then the high side pressure starts to come down slowly to about 80 psi and discharge pipe gets a little cooler.

At first i though blockage in the system caused by moisture, but wouldnt the discharge pressure go up instead of going down in this case,or am i getting my wires crossed? maybe valves in the comp? any help would be appreciated, thankyou.