Instrument cluster/HVAC lights work intermittently.

What is your question?

It seems, that when the weather is hot, my dash lights don't work. The lights in question include ALL the instrument cluster lights, the lights behind the HVAC and radio controls as well as the lights that illuminate the gear selection. These lights should come on when the headlights are turned on, but they do not. Occasionally when the lights DO come on, they won't turn off when the headlights are turned off. I have checked fuses, logic dictates that if it were a fuse, then the lights would not work at all. What possibly could be causing this?