86f250 xlt ext cab 4x4 t19 6.9

New wiring issue and as usual I don't know where to start

I have noticed that when my key is in the off position all my lights are brighter and I'm not talking just a little

Example brake lights kinda look like running lights!

I did recently loose my driver side front marker/turn light to corrosion haven't changed it yet but the wires are taped off so nothing is touching

Turn signals aren't working properly for either direction

Marker lights also dim even though they are not hooked to the stock lighting system anymore (switch went bad, ran a wire on toggle switch, also dim with key on)

Idk where to start any ideas would be greatly appreciated... Also I have to keep this truck going it was my backup for my dd 96 Audi a4 Quattro but I just had slave cylinder issue that squirted clutch and now my clutch is fried!

 

Forgot to say that the reverse lights are staying on also!....

 

Grounds, grounds, grounds. Whenever you have weird electrical problems start with grounds. Battery to block, block to frame, block to cab, bed to frame, etc.

 

I will check clean and replace all my grounds if necessary

 

Definitely a ground problem I ran a new block to frame and it helped for a few but I need the truck and I ran out of time for the night so I cut the ground wire to my tail lights and grounded them to the body! And tail lights are now back to 100%

Where is the main harness ground at? I wanna check that but I have no clue where it's at

 

There isn't a ground in the main harness, that's a European thing, American auto manufactures rely on the chassis for ground. Which admittedly probably wasn't the greatest idea.

For the rear there is a bed to ground strap, and the ground wire to your taillights comes out under the bed in the back and grounds to the bed.

 

Darn I was just hoping!... I have everything working good! Just rather have it closer to stock I don't like hacking up the stock harness but i am getting tired of doing it

 

All the harnesses on these trucks run "master" ground wires in the harness, they do run taps off to the body along this ground wire. For example, the engine bay wiring harness on a bick nose starts at the battery with a single wire plug to battery ground, then its tapped off and screwed to the passenger fender, then runs across the rad support and tapped off again on the drivers fender, then another one where the cruise mounts to the cab.

If you take the harness apart you'll find one large ground wire the whole way threw. The frame harness has a ground in it also, if you DON'T have a dully or factory trailer harness, there is no ground at the back on the last cross member, if you do have a dully or factory trailer harness, there will be a white ground on the last cross member that's for the trailer ground and dully lights only. The ground that would be one of the most important one would be the upper fender/cab ground where the cruise would also be.

There is also a ground wire that goes through the firewall plug too.

I'm glad that Ford did run a dedicated ground wire on the frame harness as the corrosion factor is greatly reduce or eliminated.

 

Thank you for the info