96 Explorer AC Problem Help

[IanL]

Problem Child
96 Explorer, 4.0 Eddie Bauer, 101,000 Miles

AC compressor does not engage. Ambient Temp. 90DegF,Low port pressure 55 psi, High side 60 psi.

I shorted the low pres. cycling switch and the compressor engaged and went into short cycle mode ( cycling off the high pressure switch, even though gage never went above 60 psi), the low pres gage went to 60 psi compressor off to18 psi compressor on. I assumed this meant low on freon.
This evening as I prepared to add freon the compressor will not engage even with the low side cycling switch shorted. I have 13.5v at the cycling switch but nothing at the clutch. Are there any other system permissives that would interrupt voltage to the clutch.
Also, does this thing have an orfice valve or an expansion valve, as I understand an expansion valve is a dealer installed part i.e expensive.

 

[IanL]

update

Blown fuse was the cause for loss of voltage, now back to to the problem.
As I said before the pressure readings would seem to indicate a low charge, and the clutch will only engage with the low pressure switch shorted. I added 12 oz of freon and the readings were as follows; Amb. temp. 80 Deg. F, Low port 45 psi, High Port 100 psi. system then began to cycle on the high press. switch, 2 seconds on, 2 seconds off. system will still only run with low pres sw shorted. All of a sudden it sounded like a vent or rupture disc relieved but the high port reading never went over 100 psi. Shut everything down not wanting to blow something

 

[IanL]

update

While replacing all ac parts I noticed an interesting item. There was a plastic cap, like the one you put on a piece of copper tubing to temp. seal it, in the suction port of the compressor hose assembly. I think somebody did a compressor r&r with a rebuilt and forgot to remove shipping plugs. After recharging the system I now have a major flow restriction. It seems the high pressure hose between the compressor ( about two feet) and the condensor is plugged. Maybe another shipping plug?
My question is is it safe to try and rod the hose out. 150 psi air does nothing and a new assembly is $115.00