66 headlight/running light problem

[Steven Hinkle]

I just developed a little (hopefully) electrical problem with my headlights and rear running lights. Hopefully, one of you folks have either had or maybe know what my problem is. I found out that my dim headlights do not work along with my rear running lights. When I hit the dimmer, it get high beams. My brake and turn signals work. I assumed it was probably my light switch so I replaced it. No fix. Then figured it was my dimmer switch which I replaced. No fix. I replaced the dash wiring harness about 6 or 7 years ago so it seems to be in pretty good shape. Does this sound like maybe a short somewhere or another electrical component giving me grief? I also completely rebuilt my steering column/turn signal switch and wiring a couple years ago. Any thoughts or advise would be greatly appreciated. On the bright side, I can still drive it during the day!

 

[Lakeroadster]

How rusty is your truck? Ground issues are typical... try this, take a 20 ft long piece of 12 gauge wire and attach one end to the ground of the truck battery. Now touch the other end to the headlight switch bezel and see if that corrects the issue. If not touch it to the dimmer switch and try again. If not touch it to the tail light housing and try again.

Decades ago my Grandfather had similar weirdness going on with his mega rusty 1970 C20... Running a 12 gauge wire from the battery ground to the tail light fixed all the issues.it was