My compressor is not engaging, fuse good , bench tested relay that's good.
low side pressure with engine off is somewhere between 50 and 100. I do ac work but my don't have a set of auto gauges so am using a very basic gauge for charging. It is brand new so probably pretty accurate.

So my question is at what pressure does the low pressure switch open?
Also is the control mounted on the charging tank the low pressure switch and if so is it a simple open or close set of contacts or is it reading resistance and tying into a computer somehow,

R134A
2006 express 3500

 

i'm not sure it this is comparable but for my 2000 sierra which uses a cycling clutch orfice tube system; the low pressure cut off is 25psi...then turns the compressor back on at 46psi.