ok guys. I have a 12 or 12 1/2 ton rtu with three compressers. it is split into 2 stages 1 stage runs 1 compresser and the other stage runs the other 2 compressers that are tied together with about a foot of pipe and go into 1 manifold. the stage with one compresser runs great. the stage with 2 compresser i am not getting any movement out of my gauges at all (nothing). the service ports are on the manifold after both compressers so there is only 1 high side port and one low side port. I dissconnected the wire for one compresser to stop it from running and still no movement in my gauges and then hooked it back up and did the same thing to the other compresser and still no movement in my gauges. amps are great! it is 3 phase. all my phases are good like i said the other stage works great and I have good amps on all the legs of the compressers that just are not pumping. I am almost sure both of my compresser have bad valves and I ordered 2 new compresser because that is the only way york sales them alreay put togeather. but before I buy them do you guys think there is any thing else I should ck. (contactors are pulling in, amps on comp are good on all legs, it is full on r22 my low side is on retard and my high sid is at around 150, it is a 95 year unit. there is just no movement in the gauges AT ALL when they are running. They are not scroll compressers where the phase could be wrong. do you guy think it is bad valves also or does it sound like I am missing something. Thank You very much for your opion.