I am working on walk in freezer R404A Air condesing unit ,it was short cycling for 5-10 seconds. The H.p was once 300psi, L.P was 0. upon playing W/ the dual pressure switch ,system would kick in, clean cond coil H.P drop to 200 Psi. Then I close liquid line service valve to pump down system it stops but when I open L.L service system dosent kick in. it only cycles for a few seconds. I changed start and the run capicator . which shorted out the start capicitor again L.P was 115# H.P was 200#.I lowered the S.P and changed the start capicator it still does the same thing. I put TXV bulb in ice cold water as box temp was over 80*. Any advice or assistance would be appreciated. thanks