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Headlights, Dash and Running Lights Problem


Well-Known Member
Local time
6:54 AM
Nov 3, 2021
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Boston MA
Pretty stuck on this problem. I just replaced the headlight switch and my dimmer switch is bypassed (the connector is jumped). If I fully engage the headlight switch to "on" I lose the dash and running lights. If I back off a hair from its full engagement it works. But that's not a fix obviously. I made a quick video. Any help would be appreciated before I resort to jumping off the headlight switch.

Ok here is me testing the old switch (the new one behaves identically).
I'm taking a guess here that:
B1 is main Power
H is Headlights
B2 is to Dimmer
P, R ????


So I could run a bypass from H to B2 to "hack" a solution at least for driving purposes but I'd much rather figure out what is going on.
Marked up the wiring diagram.
B1 is definitely hot, coming from a splice that includes the Alt battery post (Red).
B2 has to be live to finish the tail lights circuit containing the fuse (Blue)
R has to be live for the body wiring for the tail lights (Yellow)

The dimmer is inline with the fuse for the dash lights (Green)

So that means R feeds the dimmer (Yellow) not B2.

So the hack would be to jump B2 and R with H and leave the dimmer harness jumped as it currently is.

Last edited:
Well there she is folks the 10 cent paperclip jumper fix. Terminals R, B2 and H are now one. I call it an informed hack. Works like a charm and I even have a proper dimmer switch since that jumper wasn't required. There was never a dimmer problem. The middle position of my tri state light switch doesn't do anything anymore but with headlights on I have running lights, a dome light option and dimmable dash lights now. Unless someone has any informed input I'm calling it good.

Back in the day they took a 1N4007 diode and jumped the headlight to park light circuit circuit. That way you still had park lights available.
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