95 k1500 Headlight switch keeps burning.
 

So my dad is having some issues with his light switch. It keeps getting hot to the touch and you can smell burning wires under the dash. He had this problem before and went through about 4 headlight switches, After I heard about the problem I helped him wire up a headlight relay, and viola problem solved! However, now a year later the switch in the dash is back to heating up again, and smells like burning wires, only when the lights are on. He does have cab lights and marker lights below the tailgate, nothing else is on this, and ll these lights run off the relay now.

I am just wondering what else you guys think this could be? Obviously it is not the switch anymore and something else has failed allowing too much current to get this far. No fuses blow either, and the truck is a 95 GMC 1500 with a 305.

Thanks again.