Trailer wiring kit for 71 fj40? (1 Viewer)

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Hi all, I'm looking to get a trailer light hook-up going on my truck. Is there a kit readily available to do this without having to splice into the harness? I had a look at Autozone but I felt a bit confused and thought I would put it to the experts on here. I guess what I need is a 4 pin flat connector, if that's the correct terminology.

Cheers and thanks.
 
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Since you have an early 40, you don't have to worry about a 5 wire to 4 wire converter. Wiring up a trailer plug on an early 40 is pretty straight forward. Get a wiring diagram for your rig and tap into the corresponding wires(signal, brake, running) that match color/function on the trailer plug. I hated to cut into my original harness, but I soldered in a flat 4 trailer plug on my 71. I used water proof bullet connectors so I could remove the pigtail/trailer plug if need be when not in use. My camper doesn't have much draw on the '71s stock electrical system and I only have to power the brake/taillights on the trailer. This is the only thing I'll ever tow with this rig and I don't ever plan to tow at night, so this was a good solution for my purposes.

image.jpeg
 
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I love seeing old Cruisers with no roll bar. I don't know if they were all like that but mine was also without one when I first got it. But when I was 17 I absolutely HAD to have a roll bar in there as they proved my manhood. So now I have one. I just plan on towing a trailer to and from the town dump and perhaps a couple other things here and there but yeah, never at night and just want the signals and brake lights so I don't get a ticket…or cause an accident. I do have some empty connectors right where the trailer hitch is and haven't looked to see what they are all about….maybe for the license plate light, which I don't have. I hate messing with the lights…one wrong move and your horn becomes a brake light, the wipers the high-beams.
 
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Early 40s didn't have roll bars. I do feel a bit exposed, but this rig is mainly a Sunday driver. I do have the original doors and hard top for it, but agreed, there is something cool about these old rigs sans roll bar.
 

shipmag

Hagler Technology LLC. Aka Shipmag
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If I remember right coolerman has an adapter to plug into existing harness for towing a trailer. Its been a while for me but check with him.
Shipmag
 

Living in the Past

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Pretty good thread on trailer lights. It covered thiend I cleaned up the wiring on my 70 where the original cut into it. I used bullet plugs from Mark (cooleman) forr my new trailer light plug. My flasher is two weak to handle the extra plug. Plan is to use a converter that has it's own circuit fused off the battery. Only thing different is you don't need to use wire from the brake light. When I'm on a computer and not a phone I'll link the converter. Have it saved on Amazon, pretty cheap.
 
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Pretty good thread on trailer lights. It covered thiend I cleaned up the wiring on my 70 where the original cut into it. I used bullet plugs from Mark (cooleman) forr my new trailer light plug. My flasher is two weak to handle the extra plug. Plan is to use a converter that has it's own circuit fused off the battery. Only thing different is you don't need to use wire from the brake light. When I'm on a computer and not a phone I'll link the converter. Have it saved on Amazon, pretty cheap.

Awesome!
 

Coolerman

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When I build rear harnesses for FJ40's (late 74-78) with built in trailer plugs I will only use the Curt powered converter Part #56146 available from e-trailer.com for under $30.00. It completely isolates your FJ40 from the trailer. There is a separate fused power feed from the battery to the converter. This means your trailer lights are as bright as they can be and don't dim down the FJ40 lights when you hit the brakes or use the turn signals. I even make the converter part of a removable pigtail so that it's only in the elements when towing and in the glove box when not. This converter is not needed for the 63-early 74 FJ40's since they are wired the same as the trailers.

If your 71 harness is OEM, it will have a bundle of bullet connectors in the middle of the rear harness between the tail lights. These have all the signals you need to add a trailer connector without having to cut into the harness.
IMG_1725W.jpg


Green/Orange is left turn/brake
Green/Yellow is right turn/brake
Green is park
Red/Blue is reverse for trailer
 
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Living in the Past

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I even make the converter part of a removable pigtail so that it's only in the elements when towing and in the glove box when not. This converter is not needed for the 63-early 74 FJ40's since they are wired the same as the trailers.
Thought about getting a set plugs that match the tail loom connector on the firewall. Then plug a small loom that that has the signals for the Curt controller. Run the trailer light loom form there back. Then the controller could be mounted in the glove box. While a converter isn't needed on pre 74 models adding it and ignoring the brake signal you get the advantage of the later style. This will also work back further then 63. While the lights were smaller they wire the same. May had different plugs but still work the same. Believe the plug at rhe firewall is the same on my FJ25s as my 68 FJ40.
 
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Thread revival.
So where is the best place to splice into the harness?
I understand the benefits of the direct power source but you still have to manipulate your existing harness a bit correct?
 

Living in the Past

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Thread revival.
So where is the best place to splice into the harness?
I understand the benefits of the direct power source but you still have to manipulate your existing harness a bit correct?

What year? You shouldn't have to splice into the factory wiring. There should either be a single plug or bullet connectors to make your connection for trailer lights. You also should run a fused wire from the battery to the back so the trailer light load is not not the factory wiring. As mentioned use a kit to do this.
 
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78. When I rebuilt the harness there were some bullet connectors that were unused. Up by the reverse switch connector from what I recall. I'll check and see. Thanks for the info.
 

Living in the Past

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My 76 has a green plug in the middle of the rear frame member. Would have to check my 79 to see what it has. It had trailer ball bolted to the four holes in the center When I bought it but don't remember any trailer light plug. :hmm: Closing in on all the parts for it restore. Plan is one of those pintle hooks that have a 2" ball on the end. Doesn't hang below the rear frame member and will work with my 1/4 ton military trailer and trailer made from a early seventies Toyota pickup.
 

Coolerman

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Your 78 will require an intervention. :hillbilly:
Not all 78's came with the 2 pin connectors in the rear harness for a trailer hookup. The ones that don't have the 2 pin connectors, will only have a single bullet connector with green wire. This is the park circuit. In a pinch you could at least have park lights on the trailer by making a connection from this bullet connector to the BROWN wire on the 4 pin trailer plug. You would also need to ground the truck frame to the WHITE wire in the 4 pin trailer plug.

Be aware that the later rear harnesses are NOT color coded to the schematics!
Here is the color code used on these harnesses

Red = Left Turn
Yellow = Right Turn (Note this may appear to be tan or dirty white)
Green = Park/Tail
White = Brake (Note this may appear to be yellow or tan)
Blue = Reverse Lights

To add a full blown 4 pin trailer connection requires that you splice into the rear chassis wires and add the trailer converter. When you splice into the harness make sure to splice it on the PASSENGERS side BEFORE the split to the passengers side tail light. There you will find ALL the wires. If you do it on the drivers side you will not have access to the yellow wire for the right turn signal.
 

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