My clutch was not cycling off, I tested the pressure switch and it was bad. I read the service manual and it seemed that I could change the switch with the system charged. Unscrewed the switch, took it to Dodge and purchased a new one. However, now I can't thread it back on the accumulator without the o-ring blowing out from freon pressure. I have tried several different new o-rings, lubed and unlubed. Even tried the old one. no luck. Do I have to evacuate the system to get the switch on? thanks.