Tried So Many Things But No A/C in 1999 GMC Sierra K1500 Classic

[GoToGuy]

A breakthough, I got a piece of long copper wire and I touched it to the negative terminal on the battery, I then brought the other end of the piece of wire and I pressed it into the relay socket on the pin that's supposed to be ground while the relay was installed into the socket and the A/C Compressor turned on. So I guess it's time to check out the wiring or wherever that ground is.

You were advised in beginning about checking the ground points. You have the service manuals , the ground point locations are ALL shown in the descriptions and in cutaway diagrams. It's your choice to guess and randomly change parts, success eventually.
Did you ever open the service manual?

 

[marvin5881]

I didn't know the service manuals were available on the web until now, thanks. I'll make sure to post the solution once I start working on the Truck again.

 

[marvin5881]

This entire time, the previous owner promised he replaced the system properly as he was a mechanic by trade. I finally got the service manual for the GMT400 today and I realized that the A/C HIGH PRESSURE CUT OUT SWITCH that is located on the very rear of the compressor simply wasn't there. I was so confused this entire time, I really thought there was just two pressure switches and people online were confused when they mentioned a high switch and a low switch on the compressor. It turns out I was the one who was EXTREMELY confused and there really is 3 of them. After searching for a while I found the wire for the high pressure switch crammed into a nook on the side of the engine and I jumped it and now the A/C turns on. I just need to buy a new switch to put on the back of the compressor now and I should be done!

I used the diagram in the 1999 service manual for C/K trucks.

 

[LovesDunes]

"I used the diagram in the 1999 service manual for C/K trucks."

Can you post that diagram?

 

[df2x4]

"I used the diagram in the 1999 service manual for C/K trucks."

Can you post that diagram?

The '99 GM manuals can be downloaded here for free, there's a stickied thread at the top of the "Engine Performance + Maintenance" section. The links to the '99 manuals are on page eight.

https://www.gmt400.com/threads/88-98-service-manuals.43575/page-8

 

[LovesDunes]

Thanks