1970T Wiring Question.

[ARCSinAK]

Does anyone know were the split occurs in the wiring harness for the rear tail, brake, reverse and turn lights. I checked wiring diagram and there is only one hot coming from #8 fuse for both of the rear light assemblies. I see the harness coming through the passenger rear fire wall, then there is a group of wires branching off to the passenger rear light assembly/ 5 pin plug connector above the engine mount. The harness continues to around the back of the engine to the CDI box ect and then the same size approx 3/8" group of wires comes out for the drivers rear light assembly plug. The problem is I do not have any lights on the drivers rear but all function on the passenger rear. Am I correct that only one fuse controls this hot wire and at some point it splits into two for the rear lights? Where does this occur? Is the a plug connector or are the wires spliced? Don't want to go cutting into the sheath looking before I know how this system was designed. I sure appreciate your time and input.

Regards-

JS

[Mr.Doback]

Hmm, I am not the best resource since I am still new to these cars, but the harness splits off on the drivers side firewall, routing along firewall and passenger frame rail to the passenger harness plug that goes through the frame to the taillight housing. The drivers side harness goes along drivers frame rail to the plug in the body, then exiting to the drivers side taillight housing.

As far as I know, there aren't any plugs, but let some of the more experienced chime in.

[Two Rivers]

Splicing is at the right rear 6 pole connector where it goes into the body or close to it. Also # 5 and 6 fuses control the lights you mentioned

[mspirito]

It is not a single hot wire there are 5 wires going into the plug each with a different function, brake, back up, running, turn signal etc. Get a tester and try a function and see if you get any voltage.

[mspirito]

Probably a ground wire loose.

[ARCSinAK]

A loose ground wire before the plug connector in the back that only effects one side? I have tested for voltage and I have it on the passenger plug but nothing on the drivers side plug. Where are these ground connections? I only see the groung for the housing. I understand that the multiple wires control each function, I have tested the plug none of the terminals are hot on the driver side plug. The passenger side rear plug is hot and when I plug it in those lights work fine.. The wiring diagram designates fuse box 1 # 8 is for brake, blinker, backup lights. There are not seperate fuses as there are for the front turn signals, fuse box #9#10. If do not have power to any of the points in the plug before the drivers rear light hosing but I have power to all of the passenger side plug terminals and those lights work, where to I look for a bad wire or connection. How do each of those five or ten wires if you are talk about both rear light housing get power off of one fuse? I looked under the dash/steering wheel and found a number of plugs style connections/junctions there, all were plugged in. Arer there two seperate strands of wires foreach of the rear light housings? I see one splilting out of the main harness as it exisits the rear firewall on the passaneger side and it goes to passenger rear ights. The thick harness continues around the back of the engine and then sperates into CDi ect. Then I see the same size, about 3/8", of jacketd/banded of wires going to the driver rear plug connector. My question is where do these seperate bands attach to in the front of the car? How do they both function off of one fuse? Does this fuse provide power to a junction box or connector where the two bands originate and then travel together in the main harness back to the engine room? At some point these wires must branch off and go to the switches for the lights ,brake pedal, turn and trans for reverse lights. Stoked for all of your help hope this last post makes my situation clearer.

[E Sully]

The feeds to the housing for the running and directionals are separate feeds. The brake and reverse lights are common feeds spliced inside the harness. If they are all not working on the drivers side, but functiion on the passenger side, I would think the ground would be the problem.
Point 89 is the ground that is connected to the chassis behind the housing. Pull out the housing and check and clean the terminations on the chassis and housing. One way to check would be to Use a meter at the 5 pin chassis connector and check to a good chassis ground to see if you have voltage there. It would be a good time to check and refurbish the housing also.
A little cleaning, metallic paint and terminal cleaning.

[ARCSinAK]

Hi ED
I have checked the housing, sockets and the housings groung to the body. Problem is I do no have any power to plug before the housing. 85 in the diagram. Sholdnt I have voltage to those pins when the lights are turned on even when it is not hooked up the to the housing?

[ARCSinAK]

Should there be two wires connected to the ground point at 89 not just the one connected to the housing. I will look on the functioning side when I get to my garage.

[E Sully]

I would think you must have a ground issue if the harness has not been cut. As far as your testing goes, are you putting one lead directly to clean chassis metal when checking for voltage at the connector pins?
There are 2 brown ground wires in the harness. One lead is for the optional rear fog light tail, the other goes to the housing rear cover internal ground tab, while the loop grounds the outer housing with the chassis. There are 2 wires crimped under the chassis ground loop shown in the left side of the back housing picture. The loop must be sandwiched between the housing and chassis by the mounting screw. With out this secured, the lamps have no good ground. The ground from the rear cover to the housing is poor at best.
The brake lights are common from the brake switch to where they are spliced in the rear main harness. If one side works, the other should also. The reverse lights feed passes through the 14 pin connectors on the rear electrical console to the engine harness where it connects to the back of the transmission. The wire from the switch comes back through the 14 pin connectors and is spliced at the split to left and right side. Again, if one side works, the only thing that would stop the other side is a bad ground or the harness is cut.

[ARCSinAK]

Thanks Mr. Sully-

I have only one brown wire coming out of the harness after the pin connector connected to the body. There are two unconnected wires coming out the harness before the housing, a brown wire and green and white wire that are taped off. The brown one must be for the optional rear fog as you mentioned. What is the green and white wire for? Should there be two wires coming out of the harness before the housing that are attached to the body for ground?

[ARCSinAK]

[ARCSinAK]

The brown wire connected to the inside of the housing male tab goes to the 3 way crimped ground junction and then goes between a bolt that connects the bumber support to the tub for ground.

[Fastdog911]

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[E Sully]

One of the first things I will recommend is that you clean the important electrical contacts. All the rust and corrosion over the years prevents good electrical flow. A pencil eraser is good for this. Remove the light bulbs from the housing, and use the eraser to polish off any corrosion on the contacts inside the socket. Clean the pins on the bulbs also. Do this with the male pins on the 5 pin connector, and take a small piece of some fine grit sandpaper, roll it like a straw and clean the female side of the 5 pin connector.
The housing itself is the ground connection, so using fine grit sandpaper or a wire brush, clean the outside of the housing where it screws to the body. Also sand the edges where the back cover meets the housing. The brown wire that connects to the bumper support should be removed, clean the area where the wire connects so it is clean shiny metal, and reconnect. You can give it all a light spray with electrical contact cleaner at the end
The 2 loose wires, brown and green with the connectors, are spare if you have no rear fog light. Tape over the ends and Tye wrap them so they are safely out of harms the way.
I'll also recommend removing the fuses one at a time and cleaning the fuse panel contacts and the ends of the fuses. If the copper strip on the fuse looks corroded, replace it with a new one.

[E Sully]

Basic DC, the electricity travels from negative to positive. The battery "-" connects to the chassis, making it part of the circuit. If the chssis connection is not good, it will not work.
One of the problems with this housing is the brown ground wire connection to the back cover. If there is corrosion between the cover and the housing the ground connection will be lost. In this picture you can see that later on the brown wire ground point changed to the housing itself for a better ground.
When you test the pins in the connector for power, you need to make sure the black lead of the meter is connected to a good clean bare metal chassis point.

In this picture, the red arrow points to the wire brown that connects to the chassis. It must be connected to clean bare metal. The yellow arrows are the points where the screws attach the housing to the chassis, make sure it is clean where the housing touches the frame to improve the ground connection. The 2 leads in the green are the optional foglight. Brown is the "-" lead and green is the "+" lead for the optional fog light,tape it over and tuck it away in this case since no rear fog light is installed.