Dash Lights don't work when headlights are on.
 

I have a 2002 Blazer and I just got it inspected for tags. One of the problems I need to fix are the dash lights. They work like normal except when the headlights are on then the dash lights go off. I'm thinking a relay maybe? Has anyone had this issue and how do I test and fix it.

Thanks.

Have you checked your dash lights dimmer switch? That's where I'd start.

Might also check for a high resistance ground. Are your dome lights affected also. Or low capacity/weak battery.

It's not the dimmer switch and no the dome light is not affected, New"ish" battery.

Thanks, keep the ideas coming.

The rheostat next to the headlight mode switch is 'open'. Day time running light relay fail.