hola
I have a 2005 Envoy..since I bought it new the vehicle presented problems with the rear a/c not working and when this happens the front a/c (manual) blows cold air only (it can not be regulated) also the damper for recircling does not activate. The first like 8 times they would change fuses,also the blower assembly was changed. The last thing done in march 2007 was replace the block assembly,wiring harness junction engine. This worked until now. What fuse should I look for, and how doI know if this fuse box is ok?

The fuses are under the rear seat, look in the owners manual for the proper fuse and it is indicated on the cover for the fuse box.

I have checked those and are good, I thought there were more a/c fuses in the other fuse box under the hood

If there are they are indicated on the cover, no?