Dash Lights And Climate Control Issue

[cburnscrx]

Okay, here's the situation, I have a 1992 Chevy Cheyenne 4.3L W/T 2WD. As it sits now, ALL my lights work, except for the dash lights. When I turn on my headlights, the dash lights don't light up at all and the once illuminated HVAC goes blank. If I turn the headlights off, the HVAC display lights right back up. Also, the HVAC works the whole time, it's just not illuminated when the headlights are on. Everything else works exactly as it should.

 

Of course I went the overly expensive way of testing things...I replaced the headlight switch, dimmer switch, AND the HVAC controls (with the correct year and model). Whats left to check. I have checked the fuses in the dash a couple of times and nothing is blown, is there something I am missing?

 

Thanks for your time and response.

[cburnscrx]

No ideas? Am I going to end up taking this to a shop and they are going to charge me hundreds of dollars in "diagnostic" fees? Somebody has to know something about this?