Where is the A/C Relay

[Man In Black]

On my 93 Sierra pickup I'm not getting any power to the air condition compressor clutch. The fuse is good in the fuse panel and the wiring diagram is showing some kind of a relay for the compressor with four wires going in, and there is only two wires going into the compressor clutch and I don't have any power at those with the air turned on, and the clutch won't kick in. I can't find the location of that compressor clutch relay, anybody know where it is located so I can trace the power to and from it ?

 

[dirtclod]

MIB, you should check the low pressure switch at the accumulator/dryer first. It's the quart sized aluminum container close to the firewall.