I have a 80 300td with delco compressor.I decided to change over to the type 134 freon.I installed more than enough to make the pressure switch on the drier engage the compressor clutch.It would not.I pulled the wires on the pressure switch and connected them,this should have made the clutch engage It did not.I went to the connections on the clutch put current to the connection,and the clutch worked fine.Somewhere between the pressure switch and the compressor clutch,something is stopping the current flow.I have the service book,but am not worth a darn at understanding it.Please help.