Working on a subzero res refrigerator and getting 240 psi highside and -(neg) 3.5 to 0 psi on suctionside. When using vaccum pump heard a loud thump from compresser never heard that before also switched out filter drier as I couldnt get system to equilze with nitrogen thinking there might be a restiction , main concern is why on this r-12 unit would I see these pressure after charging. I never seen 0 psi with highside as high as psi was. Also can get comp over 2.6 amps when correct amps is 7.0 amps