Can anyone verify for me if the AC system on this truck has a low AND a high pressure cut out switch? I'm pretty sure the low pressure switch is right on the expansion valve going into the firewall but where (if there is one) is the high pressure switch?

I can't find an AC schematic for this thing anywhere, the Hayes book I have has barely anything about the AC system, not even a wiring diagram....

 

Well, first, I'd pick up the Factory Service Manual.

Bishko has them new; Ebay has them used.

But to the best of my knowledge, if it did have a high pressure cut out, it's on the side of the expansion valve (the low pressure switch is on the TOP).

I don't have a 1991, but for 1988 (which your system should resemble!) they don't. For 1995, they do, and it's mounted on the compressor. (1995 also has an orifice tube, so there's that.)

Sorry I can't be of more help, but at least there's that.

RwP