Swapped wiring harness, nowI the brake lights don't work

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AwesomeJ10
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Swapped wiring harness, nowI the brake lights don't work

Post by AwesomeJ10 »

I found a good wiring harness and tilt column from an '89 waggy at the yard, then put it into my '74 J20. The swap went pretty well and now everything works except the brake lights.

Turn signal lights both work and so does the hazzard lights. tail lights, head lights - everything. The turn signal, headlights, etc wires all 'just worked' without having to modify anything. They all just plugged in, mostly because I also swaped in the steering column.

All the fuses are good and pass the continuity check on my multimeter.

I guess my question is this; how does the brake light system work? The switch is good and so is the fuse.

I've looked at the wiring diagrams here (but they don't have an '89 harness)

http://oljeep.com/gw/elec/GW_wiring.html
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Stuka
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Re: Swapped wiring harness, nowI the brake lights don't wor

Post by Stuka »

I honestly cannot recall exactly how the brake system works. But I would do is take a multi-meter and start checking for voltage down the line until you find out where the signal is not getting through.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

Topic author
AwesomeJ10
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Re: Swapped wiring harness, nowI the brake lights don't wor

Post by AwesomeJ10 »

Well I figured it out.

The stop light switch energizes a light blue wire with a black stripe on it. That wire leads to the engine harness (for a reason that I don't know) and then it's supposed to connect to a light green wire with a black stripe. That light green wire goes back into the cab and connects to the steering column.

I simply tied the light blue/black stripe wire to the light green/black stripe wire to fix it. :D

Now the brake lights, T/S's etc work. :lol:
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Stuka
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Re: Swapped wiring harness, nowI the brake lights don't wor

Post by Stuka »

How odd. Glad it was an easy fix!


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2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ
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jaber
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Re: Swapped wiring harness, nowI the brake lights don't wor

Post by jaber »

I had a similar issue when I did an 85 GW harness into my 75 J-20. No brake lights. I just ran a hot wire to the brake peddle switch and cured mine.
Next is making the doors work. I cant decide on doing the whole door, or just the electrics (locks and windows).
Jeff

'46 cj3a
'51 Willys p/u
'51 Willys Parkway Conversion
'74 CJ5
'75 J-20 Wrecker
'75 J-20 Cummins service truck
'77 J-10 p/u
'79 Cherokee
'88 Grand Wagoneer
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HOOT
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Re: Swapped wiring harness, nowI the brake lights don't wor

Post by HOOT »

There is a dash switch change somewhere in the years. If you put in the wrong switch you will get this same outcome with the brake lights.

This may of been what happened with your harness swap. :-?
1980 and 81 J20 melding into a 1980 Utility bed J20. Project cancelled and for sale, found a factory truck.
1980 J20 Utility truck. Replaced above project.
1977 Honcho getting turned into a 1977 J20 Gladoncho.
IFSJA Member #4662 Joined March 28, 2003

We're on a road to nowhere.....
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