I have a 2001 Tahoe 5.3L LS that I just had a new compressor, condenser etc put in. It blows cold when the relay is jumped. It will not come on when it is just plugged in. We have checked the relays which are good, no blown fuses. I have looked all over Google and can't really pin point an answer or solution. Thank you

 

the pcm commands the relay on...the pcm needs to see the low pressure switch closed, the high psi recirc switch open and high pressure request switch closed.

if you have the correct charge level...see if it works when you jump the low psi switch. if yes...ohm the switch..if its open..replace it.
if the charge level is wrong due to inaccurate filling...evacuate and charge the system by weight.

 

I have a 2006 5.3 Suburban with front and rear air.
link to my thread:
https://chevroletforum.com/forum/tah...-102027/page2/

The AC would work great when bypassing the relay in the fuse box under the hood. We thought it might be a PCM issue so I ordered one. Wasn't the problem. After a whole summer of using a manual switch to activate the compressor, I ended up replacing the high side pressure transducer pigtail. It's nice to finally have it working correctly again.