Hi everyone, I have this issue with my climate control lcd not staying lit when on when I turn my headlights on at night. The lcd works but this is an issue when I turn on my headlights. Anyone know what the problem might be? Has anyone else experienced this issue? Thank you for your time.

From the pics I'm seeing of used A/C Controls and the '91 wiring diagram (EL-47), it looks like the backlights are internal. About 95% of the time you'll find one of three things wrong if you open up electronics from that era. In most cases they're fixable if you're handy with solder:
1) Cracked solder joints. It's a good idea to start by retouching every joint on the board(s). Don't just reheat, apply some fresh solder.
2) Leaked-out electrolytic capacitors. Replace any which are bulged or obviously corroded.
3) Damaged circuit board traces (often accompanies #2). Repair with jumper wires.

Thanks for your reply. I'll pop it open and check it out.

I haven't heard of this one before. What happens if you turn the dimmer switch all the way up? Does the display on the radio and other lights work as expected?

I was in my car earlier today, turned the dimmer on all the way and nothing on the screen.

How about the radio and all of the other stuff on the dimmer?

Everything else works, but the shifter lights also aren't working.

Shifter lights are most likely a burned out bulb.

Do you have working lights on the HVAC control buttons or is the entire HVAC controller non-lit?