Head light switch issues 1994 B4000

[Ralph Mills]

I've been having the issue that whenever my head lights are on then my dash lights, brake lights and tail lights are not on. If I push in the head light switch just a small amount then they all work but it will be intermittent. It seemed like the switch was wearing out so I replaced the headlight switch but the issue is still the same. I'm now thinking that it could be the head light switch connector. No big deal to replace it also but before I take everything off again to do it I just wanted to hear thoughts from those more knowledgeable. Thanks in advance!

 

[franklin2]

Most likely a blown fuse. The headlights are on a different circuit than the taillights/running lights. When you are putting the switch in the middle, you are crossing up the contacts in the switch and the power for the headlights is crossing over to the taillight circuit.

The brake lights are on a totally separate circuit, separate switch, they should have nothing to do with the other circuits in the back except they may have a common ground.

 

[Ralph Mills]

Brilliant!!!! Thank you!

 

[ekrampitzjr]

Small glass fuses can fail in such a way as to give intermittent contact.

 

[RonD]

1994 RANGER, not B4000, diagram below, but might be the same

The park, dash and brake lights share the same fuse, fuse 10 in cab fuse box, 15amp
Tan/white wire to Main light switch
Light green/red wire to brake light switch

From your description, assuming fuse 10 doesn't blow, there is a poor connection at the fuse panel/fuse that can only pass a few amps, so brake lights can work if there is not any other power draw
But as soon as you add the dash and park lights the amps drop to 0 and none of them work

 

[franklin2]

Taillights are on the same fuse as the brake light circuit. You can't beat the diagrams for info. Thanks for posting that.