Has anyone replaced wiring harness lately? (1 Viewer)

[Dizzy]

I believe that in the past, there was a bit of discussion regarding OEM style wire connectors and the crimping of terminals, and the terminal removal from the connectors. I'm still consider myself virgin regarding the actual important bits that make a good harness. I do recall some of the tools being kinda not over-the-counter.

If one has to do any generic mending/splicing on the harness, I recommend non-insulated crimp connectors and shrink wrap.

I don't trust the Toyota wiring scheme. There needs to be a ground wire on the chassis of every traffic-related lamp. Also, the horns and horn relay. Toyota's updated H4 headlight relay probably isn't necessary if building it stock with new wire, but, it is an upgrade.

 

[ollanik]

I have a front harness coming but decided to pull the rear harness as well. I have a ton of extra connections hanging off the harness and cannot seem to locate a wiring diagram that matches what I have - or at least one I can fully understand. I made my own diagram based on the wiring path vs. the ones in the manuals...see picture attached. I'm hoping someone can help me identify where each wire is supposed to connect to or if it is just a spare.

 

[ollanik]

I have a front harness coming but decided to pull the rear harness as well. I have a ton of extra connections hanging off the harness and cannot seem to locate a wiring diagram that matches what I have - or at least one I can fully understand. I made my own diagram based on the wiring path vs. the ones in the manuals...see picture attached. I'm hoping someone can help me identify where each wire is supposed to connect to or if it is just a spare.

 

[73FJ40]

@ollanik

I replaced the rear and front (under the hood) harnesses on my Jan '73 FJ40.

I learned that the 1973 model year rear chassis wiring harness had wires for both the rear round combination lamps and the later model red/amber/white combination lamps. The connectors were all barrel type with the PVC sleeve insulators. This would allow for the connectors to be upgraded to the multi conductor style for the newer combination lamps just by using the different connector shells.

Here is the "parts sheet" for the chassis harness:

Note that there were different harness part numbers, even some in the same model year as components were changed.

In my harness:
G = running lights
G/Y = right stop/directional combination lamp (note there are two filaments in the combination lamp bulb, G & G/Y)
G/O = left " " " (word is that sometimes G/B is left)
R/L = backup light (you named it blue, but Toyota named it Lavender to reserve the "B" for Black)

G/B was not used (this was used in later models for left directional) You have G/Blue on the left side, but it should be G/Black.
G/W " " " (this was used in later models for both stop lamps)

The connectors in the middle of the rear bumper between the two combination lamps was for an optional trailer connector.

The four circuit connectors at the firewall (your upper sketch) have some wires that weren't used on 73 models.

What were used were R/L which went to the backup light switch on the transmission, and then the outlet from the switch went to the rear harness.

The Y/R goes to the fuel gauge sending unit on top of the fuel tank. There is also a White/Black wire on the sending unit that MUST connect to ground.

Hope this helps.

 

[ollanik]

@ollanik

I replaced the rear and front (under the hood) harnesses on my Jan '73 FJ40.

I learned that the 1973 model year rear chassis wiring harness had wires for both the rear round combination lamps and the later model red/amber/white combination lamps. The connectors were all barrel type with the PVC sleeve insulators. This would allow for the connectors to be upgraded to the multi conductor style for the newer combination lamps just by using the different connector shells.

Here is the "parts sheet" for the chassis harness:
View attachment 2880456

Note that there were different harness part numbers, even some in the same model year as components were changed.

In my harness:
G = running lights
G/Y = right stop/directional combination lamp (note there are two filaments in the combination lamp bulb, G & G/Y)
G/O = left " " " (word is that sometimes G/B is left)
R/L = backup light (you named it blue, but Toyota named it Lavender to reserve the "B" for Black)

G/B was not used (this was used in later models for left directional) You have G/Blue on the left side, but it should be G/Black.
G/W " " " (this was used in later models for both stop lamps)

The connectors in the middle of the rear bumper between the two combination lamps was for an optional trailer connector.

The four circuit connectors at the firewall (your upper sketch) have some wires that weren't used on 73 models.

What were used were R/L which went to the backup light switch on the transmission, and then the outlet from the switch went to the rear harness.

The Y/R goes to the fuel gauge sending unit on top of the fuel tank. There is also a White/Black wire on the sending unit that MUST connect to ground.

Hope this helps.

Great info - thanks