Havac weird problems

[96silvy]

So I have a 96 k2500 with the 5.7. The vents are stuck on defrost and face, and just recently the temperature gauge doesn't work. My fan speed does work however since I'm unable to to change the temp, it's constantly blowing hot air. Neither the A/C button or the recirculate work. Also I replaced the lights with leds, but they only come on when I have the lights on with the key out. As soon as the key is turned to the start position the Hvac lights go out. Any help is appreciated!

 

[97redz71]

This sounds like exactly what happened to me. I did HVAC led swap too and I can control fan speed, and no matter what setting its on, the air blows at my feet.
Did you figure out what it was?

 

[88Scottsdale]

Sounds like it appears to be an issue with your control module. I would suggest looking at the local junkyard and finding one to replace yours with. This happened to my 88 c1500 and as soon as I replaced it, all was well.