I'm trying to get the wiring done on my 76 f150 and I'm getting close but need help. I'm using tail lights that have two filaments that plug into a three wired terminal. Just by trial and error I've managed to get most things working. I cleaned all the grounds but I can't seem to get the brake lights or signals to work when the headlights or running lights are on. I've identified the three wires I have. One is hot when the headlight switch is pulled out. One gets volts when the brake petal is applied and one gets hot with the turn signals activated.
I'm wondering if someone can tell me what wires go where on the three wired connector. I've tried so many combinations but am still left without complete success. Also I am not running back up lights and I've managed to run the side marker lights independently on a hot wire from the headlight switch that I believe went to some sort of running light that is no longer there.
Thanks for thinking about this with me.

 

Something is not correct. American cars and trucks, especially old ones like yours, do not have separate wires for the turnsignals in the rear. The same wire that does the brake, does the turnsignal. So you have 3 wires going to the rear;
1. Left turn/brake
2. Right turn/brake
3. Running lights(usually brown).

So you have a dual filament bulb on each side. Each socket has 3 wires. One wire is the common ground. The 2nd wire is the brighter filament, and is hooked to the brake turn wire. The 3rd wire is the lower output filament, and it goes to the running light wire.

The running light wire will have splices and feed both sides of the rear, and the license plate lights also.

 

Aha! OK, that makes some sense to me then. I'll recheck the voltage on all three wires and identify them better. This would explain why I had the lights blinking with the signal in either direction. I must have done some amazingly intricate wiring to get all the stuff to work. Gosh, that's most likely why I was so doggone confused by it all.

So thinking here....I'm going to run the running light (hot when the headlamp swith is pulled) to one wire on each connector. I am going to figure wich signal is wich by testing volts with the indicator switch in either position and run those wires to there corresponding sides. Finally going to ground one of them on each side. According to my manual it seems to be the middle wire on the connector.

Does this sound correct to you so far? Of course I can easily just hook one side up with power and turn/brake wire activate the turn signal and see if it's the right side or not. Yeah, I had all the wires connected to one side for just testing after I started from scratch and the light was blinking with the turn signal left and right. I was baffled...I was just thinking at that point that I must have to wire everything together for it to work itself out. Wiring is a challenge for me but I really appreciate your input.

Thanks again.

 

Dave, thanks! Success at last! It's getting dark but I decided to give it one more try and by God it worked! Thank you so much for the help. I just got the driver side done so in the AM I'll button up the other side.

So the wiring is going to be the same for the other side right? All I've got to do now I'm thinking is connect the two together. Should I just run the hot wire from one tailight to the other at the same position? Then connect the other signal light to the same position as on the other side and ground the leftover one then?

Thanks again!

 

I believe you have it figured out. Each side has it's own signal/brake wire, but both sides use the same running/taillight wire(along with the license plate light also).

 

Just buttoned up the other side and it all went without a hitch...Thanks a ton!

 

Give the man some reps---if you haven't already.

He's pretty amazing in his auto electrical knowledge!

 

The previous owner of an '86 F150 installed a 351W with a C6 trans. They tie wrapped the back up harness along the frame. I cut the female end, 4 prong, from an '83 and want to wire it into the '86 to accept the the male plug, 4 prong, from the back up light switch at the trans.
Should be easy, only I can't find the two color coded wires in the '86 wire harness. There is one female rectangular 2 slot plug with a brown and black wire attached each side.
Can I use these two wires to connect the back up lights...I'm already prepared to run wire. I know there are two switches in the back up lite housing. I've ID'd which set is which. My thought here is to wire the female plug directly into the harness so I can plug in the switch male plug.
Thanks in advance for thoughts on this.

 

No matter what tranny the truck had, the backup light switch is fed with a purple/orange dotted wire, and it leaves the switch to feed the back-up lights on a black/pink wire.

I would search through the harness going to the rear and try to find the black/pink wire, and then follow it up front, it should end up at the original switch plug. There you should find the other purple/orange wire.

 

The plug on the truck side (frame) is gone altogether. I must find where and if they cut it out. I understand manual transmissions have a different set up (2 wire oval plug). I'm wondering if that is the plug I'm looking for. I'll know more tomorrow cause I'll be working on the brakes and reverse lights then. Think I'm in for a fun one with this cause there may have been a manual tranny installed previously. At least it's not difficult to access.
Thanks for the info, that confirms what I learned from the wiring diagrams.

 

All is well...just as I suspected the truck had a manual tranny at one time and the back up light switch is different. Wound up replacing the 2 prong plug, wiring in the 4 prong plug and bingo...let there be light...thanks for the assistance.