It could be a variety of electrical issues. You did not post the pressures you found....that would be beneficial. If the pressure is not high enough, the compressor will not engage. This is too prevent damage, obviously. If you've bypassed this switch and still no clutch engagement or no power then you may have an issue with the A/C On/Off on the dash. The sure fire way to diagnose an electrical problem is to obtain a wiring diagram or schematic. It would then be very easy to use a multimeter to work back from the power source (the battery) and find the break in the electrical system. Someone on this forum may have an electrical diagram of the A/C system for your year truck. You can get more A/C info from:

http://www.autoacforum.com/

but, be prepared to provide the high and low side pressures....even if the compressor is not turning.

 

what happens if you jump the a/c clutch relay?

 

clutch wont engage.. voltage on both sides of cycle switch..no signal to high pres. transducer or ac relay from ecm..i can ground relay and comp. runs....plz. help

 

My problem turned out to be a bad instrument cluster. My pick-up had automatic climate control and apparently a/c circuits are tied in to the instrument cluster. I replaced the instrument cluster and the a/c now has power and is working fine.

 

Since you FAILED to identify what you have, your comments are not useful and do not apply to the vehicle under discussion here.

Why did you feel compelled to post the same almost useless information in so many old threads?

 

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HEllo Steve very old thread but I'm having the same problem. Cannot find the schematic