1973 fj40 wiring questions

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Hi mud,

I've been working on my '73 for about a year now. We got it running and driving, and now the next step is to sort out lights/signals/brake lights. the rear harness back near the frame crossmember had been severed, so I'm trying to figure some stuff out. I got the headlights to work, turn signals to turn on in front/rear, but not blinking. I also traced down the red wires running towards the back that have power when headlights are on, so I assume those are the running lights.

the question is, can I simply run the red wires to each respective tail light for a running light, or do I need an associated green wire to be a companion there? And how can I get the turn signals to flash? I am obviously not hooking up a green wire correctly?

Sorry, I have stared at the wiring diagram and it's literally Greek to me.

thanks!

Joel
 

73FJ40

After another night of rust removal!
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Time to get your silver star so you may post pictures.

I rebuilt the rear wiring harness on my 01/73 and the running lights were solid green wire. The backup light was red with a lavender trace. If you have solid red wires, it may be a PO made some changes.
 
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Time to get your silver star so you may post pictures.

I rebuilt the rear wiring harness on my 01/73 and the running lights were solid green wire. The backup light was red with a lavender trace. If you have solid red wires, it may be a PO made some changes.
OK thanks man, with the lights on in the front, I was just trying to find wires that had power going to them at the same time for my rear running late. I will now test some of the green wires back there to see if those have power also, like you said

Wiring is not my forte! Lol
 
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When the turn signals come on but don’t blink it means you simply have a burned out bulb or a bulb isn’t grounded. Most electrical gremlins are attributed to poor grounding. 12 volts is very little electromotive force, so it takes only a small amount of corrosion to break the circuit. it’s pretty common on an old vehicle. Imagine a garden hose barely turned on, rather than open all the way. You can put your thumb on the end of the hose and stop the water. Voltage is the ‘pressure’ that moves current through the conductor. Remove the bulbs and thoroughly clean all the contacts in the sockets and the bulbs. Do the same with the fuses. Disconnect the battery before messing with the fuse block. IIRC the turn signal wires are green with a stripe. Yellow stripe on driver side and black stripe on passenger side, but don’t quote me on it. I think solid green is either brake or running lights, again don’t quote me. Good luck.
 

Coolerman

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For your 1973 rear harness:
Green/Orange is the left rear turn
Green/Yellow is the right rear turn
Solid Green is the Park/Marker/License lights
Blue/Red is the +12V input wire to the reverse switch
Red/Blue is the output of the reverse light switch and goes back to the Reverse lights
Blue/Yellow is for the T-Case switch
Solid Red is for a vacuum switch and is not used
Yellow/Red is for the fuel tank sending unit
White/Black is for Ground

If this is a true 1973 it will also have Green/Blue and Green/White wires that are NOT used so don't worry about those.

Do your Hazard lights flash when activated? If they do not AND If you have BOTH front and rear turn lights coming on when you activate the turn signals but they don't flash then you have a bad flasher.

How about brake lights? Do they work when you press the brake pedal? Remeber they share the same bulb element as the turn signals so you know the bulbs are good already. If your brake lights do not come on then it's the brake light switch. It could be bad or out of adjustment.

Hope that helps you get this sorted out.
 
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For your 1973 rear harness:
Green/Orange is the left rear turn
Green/Yellow is the right rear turn
Solid Green is the Park/Marker/License lights
Blue/Red is the +12V input wire to the reverse switch
Red/Blue is the output of the reverse light switch and goes back to the Reverse lights
Blue/Yellow is for the T-Case switch
Solid Red is for a vacuum switch and is not used
Yellow/Red is for the fuel tank sending unit
White/Black is for Ground

If this is a true 1973 it will also have Green/Blue and Green/White wires that are NOT used so don't worry about those.

Do your Hazard lights flash when activated? If they do not AND If you have BOTH front and rear turn lights coming on when you activate the turn signals but they don't flash then you have a bad flasher.

How about brake lights? Do they work when you press the brake pedal? Remeber they share the same bulb element as the turn signals so you know the bulbs are good already. If your brake lights do not come on then it's the brake light switch. It could be bad or out of adjustment.

Hope that helps you get this sorted out.
Huge help here, @Coolerman
 
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For your 1973 rear harness:
Green/Orange is the left rear turn
Green/Yellow is the right rear turn
Solid Green is the Park/Marker/License lights
Blue/Red is the +12V input wire to the reverse switch
Red/Blue is the output of the reverse light switch and goes back to the Reverse lights
Blue/Yellow is for the T-Case switch
Solid Red is for a vacuum switch and is not used
Yellow/Red is for the fuel tank sending unit
White/Black is for Ground

If this is a true 1973 it will also have Green/Blue and Green/White wires that are NOT used so don't worry about those.

Do your Hazard lights flash when activated? If they do not AND If you have BOTH front and rear turn lights coming on when you activate the turn signals but they don't flash then you have a bad flasher.

How about brake lights? Do they work when you press the brake pedal? Remeber they share the same bulb element as the turn signals so you know the bulbs are good already. If your brake lights do not come on then it's the brake light switch. It could be bad or out of adjustment.

Hope that helps you get this sorted out.

Posting on mud after over a year with no posts does this mean you all caught up? My 73 has about five minutes of work if you free to stop by.
IMG_20200923_120947210.jpg
IMG_20200923_120956535.jpg
 
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@Coolerman One of my issues is that my lights don’t blink when I turn left or right, and I also have no rear running lights when the headlights are on…

But, when I turn on the hazard switch, all of the lights blink, so that’s good.

Thanks for your help
 

Coolerman

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Posting on mud after over a year with no posts does this mean you all caught up? My 73 has about five minutes of work if you free to stop by.
View attachment 3084942View attachment 3084943

You mean 5 YEARS of work don't you? :cool: I don't think I have ever seen an FJ40 so messed up wiring wise... When you get all that ripped out, the dash holes welded up, the truck painted and are ready for a wiring harness let me know...;)

I had to stop building harnesses full time. My health issues, family issues and working a full time day job was just too much. I still sell parts, and build sub-harnesses but full harness building is simply not an option. I have taken on some wiring harnesses like the FJ28 project, and a couple of FJ25 projects just cause they are so unique.

I recently was sent an original 1973 FJ40 complete harness set. I agreed to fix the harness for the owner in exchange for the opportunity to fully document it. It is only the second time I have seen one of these harnesses. They are unique to the 1973. I am about half way done documenting it. Once I am done I will be able to answer electrical questions about the 1973 FJ40 with more confidence.
 

Coolerman

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@Coolerman One of my issues is that my lights don’t blink when I turn left or right, and I also have no rear running lights when the headlights are on…

But, when I turn on the hazard switch, all of the lights blink, so that’s good.

Thanks for your help
Well the fact that all 4 lights blink on Hazards tells you the bulbs are good (though they could be the wrong bulbs) and the flasher is good. So if you are not getting blinking on the left/right turn signals it can be a couple of things. First is to check that the bulbs front and rear are the correct ones. The flasher is a current activated device. A certain amount of current must be flowing for the flasher to flash. If you have the wrong bulbs installed, two of them combined (ie using turn signal) may not provide enough current flow to flash, but the Hazards work because you have 4 bulbs drawing cureent. Same for poor ground. Check that all four light housings are getting a good ground.

For the rear Park light issue just remember that the solid green wire carries the current for the Park/Marker and License lights. So that one wire has to go to all FIVE lights!
 
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You mean 5 YEARS of work don't you? :cool: I don't think I have ever seen an FJ40 so messed up wiring wise... When you get all that ripped out, the dash holes welded up, the truck painted and are ready for a wiring harness let me know...;)

Sounds like it should be a post in the PO hall of shame thread. Worse you have ever seen is saying something.

Before I remove the wiring for body work I plan on cleaning it up and getting it all working. I was just kidding about having you work on wiring. It’s all the holes drill in the dash that bother me. Have a background in HVAC controls. I have the patience and know when to walk away and start another day. Not something you want to rush. Had this cruiser 1994. Was offerd to me to cheap to pass up. Just wish when I picked up a 73 reverse light and heater switches from wrecking yards would have pull compete harnesses from a few. Have plenty of harness material for my 68. Have a spare 1980 harn6for my a couple of 78 harnesses to use on my FJ45.
 
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Well the fact that all 4 lights blink on Hazards tells you the bulbs are good (though they could be the wrong bulbs) and the flasher is good. So if you are not getting blinking on the left/right turn signals it can be a couple of things. First is to check that the bulbs front and rear are the correct ones. The flasher is a current activated device. A certain amount of current must be flowing for the flasher to flash. If you have the wrong bulbs installed, two of them combined (ie using turn signal) may not provide enough current flow to flash, but the Hazards work because you have 4 bulbs drawing cureent. Same for poor ground. Check that all four light housings are getting a good ground.

For the rear Park light issue just remember that the solid green wire carries the current for the Park/Marker and License lights. So that one wire has to go to all FIVE lights!
thanks!

I do have new housings/bulbs for front and rear turn signals, so it could be a ground issue...? Also, would the solid green (needing to go to all 5 lights) also affect the running lights in the rear when the headlights are on?

cheers
 
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thanks!

I do have new housings/bulbs for front and rear turn signals, so it could be a ground issue...? Also, would the solid green (needing to go to all 5 lights) also affect the running lights in the rear when the headlights are on?

cheers

Are you saying when you pull the light switch out to the first position you have tail lights, rear side marker lights and the license plate light. But when you pull to the second position for headlights they go off. If so problem is probably in the light switch.
 

Coolerman

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Running lights = Park lights
The 5 lights in the rear are
Left Marker light
Left Park light (running light)
Left License light
Right Marker light
Right Park light (running light)
All these lights are powered by the single solid green wire in the rear chassis harness.

The complete circuit is this: There is a solid green wire coming off the headlight switch. This goes to the front running/marker lights, then is spliced to the rear chassis harness solid green wire where it goes to the 5 rear lights.

FYI I can build you a new rear chassis harness that eliminates all the unused OEM wires, including the non-functional Toyota trailer wiring and replaces that with a standard 4 pin trailer connector. Plug and play for all your lights. Send me an email if you are interested.
 

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