I have a 76 f100 stepside and have a mess involving the wiring .
My problem right now is taillights and the fuse box. Are the brake lights and taillights on the same circuit? I have brake lights and no taillights. Any help would be appreciated.

 

The other half of this diagram can be found in the tech info hyperlink sticky.

 

I seem to have something weird going on.i was making progress checking circuits and gaing ground on it.Now I get nothing with test light on any circuit. Test light works engine starts turn signals work brake lights work but nothing tests with light as working.whats up?

 

Did the you blow the bulb in the test light?

 

Nope test light is good.

 

Ignore this post.

 

Thanks for the info.

 

Please accept my apology; my brain logged out for a few minutes. They are NOT on the same circuit; I gave you incorrect information and have since deleted my original post.

The brake lights are protected by the fuse panel; the tail lights are NOT. The tail lights are part of the running light circuit, which is protected as a whole by a circuit breaker internal to the headlight switch.

Do the rest of your running lights work (front parking lights, side market lights)?

What do you mean you're having a problem with the fuse box? What's the problem?

 

Well i could take mt test light and get all circuits to test.Then nothing tests out but have turn signals and brake lights and engine starts

 

I don't understand what you're saying.

 

Why would one minute i can test the circuits with the light and they test fine.Next minute nothing tests out to work but some things work.

 

You need to be more specific about what "test out" means, and what the "circuits" and "things" are. I should be able to replicate your exact measurement on my own truck without any confusion. As of now I have no idea what you're doing.

 

If I take a 12 volt test light and touch it to the terminals in the fuse block the light lights up.Then for no reasoncant get any terminals to make test light work, but i have some things working.

 

It almost sounds like you have a problem with the test light.

 

I would normally agree but when I check it n the battery it works fine. Could it be a grounding problem?