Took Floyd's rear bumper (which appeared to be a giant after market, homemade, multiple light, tow rated behemoth) off and carefully labeled all wires - six in number that ran all the way to back of truck.
Used wire brush on grinder, hooked all wires and ripped them out almost all the way back to firewall.
Have a shop manual which has a wiring diagram. Can't really make sense of it.
Tested all the wires to see when power was available, i.e. with and without ignition and light switch on, and found the following.

1 wire is hot no matter what switch is on.
1 wire is hot until ignition is on then goes cold.
3 wires that look long enough to have gone to the back are never hot no matter what I turn on.

The only two I can clearly identify are the ones to the master cylinder switch.

I don't have many strengths when working on Floyd, except patience but really have a weakness when it comes to auto wiring.

Really want to fix this myself instead of taking it to a shop and don't want or think I need a new harness.

Help?

Wires appear original and were in a cloth sheathing.

 

My general feeling is that it is easier to start over than try to fix someone else's attempt at wiring. Little good ever comes of that.

The rear of the truck only needs one wire for tail lights (from the headlight switch when on); then one wire for each turn signal (from the turn signal switch) and, depending on how it is wired, possibly a separate wire for the brake lights (from the brake switch). This is assuming you have turn signals. If no turn signals, only a tail and a brake light wire are needed.

Anything else was probably extra lights and/or trailer wiring.

Make sure you use the correct gauge of wire. If 6volt, you will need heavier wire than 12V, I believe.

 

It isn't unusual to find lighting wiring that confounds mere mortals. Often, it is best to back all of the way up and reset. What end result do you desire: single lamp (combined tail & brake light), multiple lamp (separate lights for tail/brake, front parking/signal)? What version after-market turn signal is installed? Most of the older units are limited in configuration due to the number of wires. What you have - or intend to have- greatly affects the next steps.

The solution to stock / near stock wiring isn't magic and can be attained with a few diagrams and some patience.

Which way do you want to go?

DW

 

Floyd's only mods I plan are power steering and ramhorn exhaust manifolds.
The rear bumper has a light on each side that is set back in the massive bumper and then on each side a red lensed / pedestal mount light on top of bumper right above the built in lights. The single top mounted lights have red lense on back and amber lense on front. The embedded lights are red.
The top lights have a single yellow wire to them while the embedded lights have a red and black wire to them.
I haven't had the bumper on for over a year and can't remember the function of each of these lights.
The turn signal mechanism is stock and will stay that way and I will leave the tail lights as they are.
Regarding the front lights, everything is still wired and although I plan to remove the front clip, I will put all back when reinstalling clip.

I am planning to use Floyd on country road drives, local parades and a few car shows.

He is really straight off the farm with the only improvements I can see being new vinyl upholstery and an apparent re-paint.

The wire loom (?) is intact from the firewall back past the brake master cylinder so I have good options to tie into them without going inside and under dash.

I am most eager to offer any additional information to aid you guys in guiding me.

Fred

 

Fred

Want to caution you on keeping 'some' of the old wiring and still trying to upgrade the rest. You'll tend to struggle with making the old stuff actually work. I understand the desire to retain the old loom, but keep in mind that the insulation under the dash has been deteriorating with time. The loom is reproduced and can be replaced.

In addition, the turn signal was aftermarket as well. Take a look at the name on the unit - the older ones were some version of 'Signal Stat'. Count the number / colors of wires running from the unit - it will affect the rewire configuration. You will need a diagram like this (note the wire difference):



Let's start in the front. When you say that everything is wired up, does that mean there are aftermarket lights fender mounted - like these with amber front and red rear lenses?



Are you intending to keep these or convert the parking lights into parking / turn signals? The conversion isn't a big deal.


Keeping the rear bumper certainly changes the look of the truck. Bumperless, the back end looks much different. It also lets you put the spare under the bed:

The tail lights are then mounted from brackets attached to the bed - there should be captive nuts already in place on both sides.

If you want to keep the current configuration, pics would help.

Rewiring these beauties isn't overly difficult. The wire gauges are in the shop manual / owners manual and the work is with a ruler and wiring diagram.

DW

 

My thinking is that the wiring was routed, in a manner similar to other makes of vehicles, with a hot wire going directly to the lights and then a ground wire going from the other lamp terminal to a switch that completes the path to ground when closed. So, the brake lamps would connect between the wire that is always hot and a wire that is grounded when the brake pedal is stepped on.
There were many things that Ford patented early on and I have been told by an automotive class instructor that using the car body as a common return and switching the hot (as obvious a concept as it is), was one of Ford's early patents. Thus, those who would not receive Ford's licensing to use his patent were forced to use more wire in their vehicles until the patent ran out. I don't know how accurate this is, but, it is a good story anyway.

 

I have rewired the tail lights and trailers of maybe a hundred Big Riggs.
Napa or any truck parts or trailer parts store will have a roll of what we
called 7 wire all in a harness and standered color coded. It is coded to
the trailer plug that has the color code right on it. With that ya also
have your wiring diagram built in and with ya at all times.
Ya may never use the trailer plug but it is there if ever needed. Or leave
it off completely.
And anyone can work on it and see at a glance what wire is supposed
to go to what. Because it is marked on the plugs. So easy.

 

It sounds like the embedded red lights in the rear bumper are the tail and brake lights. The pedestal lights on top are turn signals.

 

I am appreciating your help a lot. I am not certain if you are aware my truck is a 55. The turn signal mechanism seems to be factory and the parking lights/turn signal lights are part of the grill assembly rather than what your truck shows with lights atop the fender.

I do agree with you about the condition of the wires in the old loom and think I will take the time to trace each wire through the firewall and back to its source replacing each wire as I go.

Thank you for taking interest in my needs.

Fred

 

Thank you guys. Jeremy, when I look at the wiring diagram in my shop manual it shows two wires going to the back. One from the brake switch and one from the light switch. The one from the light switch goes to the driver's side tail light then splits off with one wire to the license plate light and another to the passenger side light.....then to ground.
The wire from the brake switch runs straight back to the driver's side light and splits off to the passenger side light.

I'm going to move the bumper (very heavy) close enough to the truck to use some trial wires per your suggestion and try to identify the various wires that way.