Strange Headlight problem

This problem has me confused. My 1972 Demon when you first start the car you can turn on the headlight and use the foot dimmer switch to toggle back and forth from lo to high beams. Now after you drive the car for a wile at night all of a sudden with out touching the dimmer switch the red “high beam” indicator in the dash will light up. Not as bright as when you click it normally but lit up. Once that happens the dimmer switch will no longer do anything you press it and the light just stays on and you can no longer get the headlights to toggle back and forth between high and low. I tried replacing the dimmer switch and I replaced the main light switch also and it did not change a thing. Only way to get it to go back to working is to shut the car totally off then restart it and they start working like normal again till it happen again after driving for a 10 min or so.

Has anybody had this problem? If so how dod you fix it?

Thanks