all kinds of wiring

[fordman]

Hello there,

I am having issues with my rear brake, tail, turn signals and back-up lights on my 67 F100, 4wd, NP 4spd and have seen you are the key source to helping everyone with wiring issues. It is great that you understand all that, I have always said I am Electrically Retarded, and my father who is an Electronic Engineer is 1600 miles away. Also, the rear bumper has been replaced at least 30 years ago and there is a bunch of splicing in the rear "dead space" where the spare tire would hang.

Here's my issue:

The headlights, parking lights and turn signal lights in the front work all as they are supposed to.
The rear lights are all awry though!

Headlights off: Nothing in the rear. No brake lights, no turn signals, no back-up light.

Parking lights on: Nothing in the rear. No brake lights, Turn signal either L or R causes a dull glow that blinks slow in both L&R taillight bulbs.

Headlights on: No brake lights, no tail lights, if the turn signal is activated in either direction, both tail lights blink.

I am thinking that I need a new reverse light switch, where would I find that in the truck or trans? I am assuming that the brake light switch is bad too, and am thinking I might just get a new brake light harness too. Am I on the right track? I have a month to figure all this out so I can get it inspected and registered.

[fordman]

dougf pmed me this and i am not 100% sure on alot of these symptoms. that is why i ask everyoen to post in the forums and not pm questions. all i can see that strikes me is the dull lighting of the lights in the rear is a bad ground issue. i would look at and straight out al of the mess of wires under the bed also. by removign what wasnt hooked up any more. the grounds can be throguh the tail light housings. and into the bumper or frame if someone has added a trailer light plug. the way to check a brake light swithc is to see if it is gettign power through it. and then up to the tss or hazard swithc where ever that wire goes after that i forget without looking at the diagrams again. anyone else want to help him out. this is all i can see from this pm he sent me.

[Thunderfoot]

I second a "Grounding" issue with the rear tail lights.

[Doug F]

OK, here's what I have done so far:

I noticed the wires going into the tail-lights is a 1970 number?!?! Must be from the bed that is on there. Underneath, there were a bunch of splices and lots of "probe" holes, which tells me that someone else had issues before me!

I took the headlight switch out, unplugged it and made sure all the terminals were clean, then put some dielectric grease on them and re-installed it. Did the same with the emergency flasher switch in the glove box, but not yet with the brake light switch.
Under the hood, up by the firewall, I found the "Black w/ Red" wire was broke in one spot and cut 3" away! Couldn't tell you why! I pieced it back together, unplugged the 4 into 4 connector running down to the rear, it looked kind of rusty? inside... Anyway, I was getting a left turn signal with the lights off, right turn signal blinked both bulbs, with parking lights on, both bulbs blinked with turn signal lever in either direction, I had one brake light that was really weak too. After all this I ended up not having anything again! W T F!!!!!

Today, I unplugged the whole rear harness, pulled it out from under the truck and am going to try to trouble shoot this standing up instead of on a creeper with sheisse falling in my eyes. The half-wit that spliced the lights into the harness just used red wire instead of Black for Black with Red, Green for Green, Yellow for Yellow and Brown for Brown. Just a little pet peeve of mine.
I will wire them up right, get everything situated and try this again, before ordering a new "Body Harness" which I can't really afford right now.

[Doug F]

PROBLEM SOLVED!

30 minutes on the phone with my father (an Electronic Engineer and old car builder/racer) figured out that the bed wasn't grounded!

I ran a simple wire from the taillight housings (both) up the harness to the firewall/engine ground. WHEW!

[fordman]

the bed grounds to the frame. the tail light housings ground to the bed via the screws to hold the tail light housings in. the frame would get a ground somehow or all of our trucks lights wouldnt work. my bet it the screws were dirty or the socket housings. you probably didnt need to run that extra wire.

[Doug F]

With all the dirty and rusty bolts and frame, I provided bullet-proof grounding. I had to re-run the wiring harness back up to the front anyway, I just tagged along a 20' run of #12 wire too.