66 C20 Dash light dimmer

[StevenG]

The dash lights come on when you turn the key to on with out the headlight switch pulled out. Is this normal?
When you turn the headlight switch it only dims the taillights. That’s not right.
Any ideas?

[ray_mcavoy]

Yeah, that's definitely not right.

Dash lights should come on when you pull out the headlight switch (even without the key on). But turning the key on (with the headlight switch off) should not cause the dash lights to come on. And rotating the knob should vary the brightness of the dash lights ... not the tail lights.

Sounds like there may be some wires crossed up on the headlight switch connector and/or elsewhere in the wiring harness. Can you see any signs of splices or other changes / modifications to the wiring?

[PGSigns]

You may have a ground loop going on. Ad some grounds to the bed, rear light buckets. hood and marker lights. See if that helps the dim lights. Then look at the back of the dash for added wires that may be screwing up the lighting circuit. I have seen some creative wiring over the years that made all kinds of things go on.
Jimmy