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99 Xj Wiring To 90 Mj Tail Light Harness


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I found a few threads here, however none of them had a finished walkthrough. I've completed 90% of my 99 XJ swap in to my 90 MJ. At this point the only electrical issue is the running/brake/turn lighting on the rear. As has been stated, the XJ wiring and socket types differ from the MJ. I've isolated the XJ wiring and MJ wiring. I have the running lights working properly. I can also get the turn signals to work properly. Where the problem comes in is when I hook the brake light in to the equation. The XJ setup uses different wires and bulbs, where the MJ setup is all intregrated. Has anyone sucessfully intregrated the XJ electrical through the OEM MJ rear wiring harness? Everything I know about electrical wiring tells me I know nothing at this point. I would appreciate any help on this as this is my last real hurdle toget the truck on the road. Did I miss an article or thread here about it? Thanks a bunch guys!

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I think I missed explaining what the problem is!!!

 

Everything works until I have all 3 thing on at the same time: running lights, brake light, turn signals. When I press the brake with the current setup, the turn signals stop completely. I assume I have current traveling back up the system and confusing the turn signal circuit, but I'm not 100% sure.

 

Hopefully that outlines my issues a bit better.

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I think I missed explaining what the problem is!!!

 

Everything works until I have all 3 thing on at the same time: running lights, brake light, turn signals. When I press the brake with the current setup, the turn signals stop completely. I assume I have current traveling back up the system and confusing the turn signal circuit, but I'm not 100% sure.

 

Hopefully that outlines my issues a bit better.

 

You have to run the brake lights through your turn/hazard switch on your steering column.

 

Did you swap the 99 column? Or do you still have the 90?

 

Here's a nice little write up for the wiring.

 

http://comancheclub.com/topic/18588-xj-dash-harness-to-rear-mj-harness-wiring-guides/

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I haven't done this swap, but I have given it a lot of thought because I think the XJ setup with separate brake and turn lamps (and 4-ways) is far superior to the MJ setup in which the 4-ways cancel the brake lights. I am considering changing mine to the XJ setup even without doing a newer-year conversion.

 

What I have in mind is to keep the MJ brake lights as taillights/brake lights. I would put amber bulbs in the backup light sockets and wire those separately as turn signals and 4-ways. And then I would add a pair of small fog lights wired to function as backup lights.

 

If you want to keep the stock backups as backups, the MJ has two stop/turn lamps on each side. It would be easy enough to split those, and run one lamp on each side as tail and brake lights, and the other lamp on each side as turns and 4-ways.

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I did what Eagle is describing. I ran another wire to the back to seperate the turn/hazard from the brake lights. I took away a lot of the headache. Now my top light in each tail serves as brake lights, the next set down from the top in each tail serves as the turn/hazard.

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You have to run the brake lights through your turn/hazard switch on your steering column.

 

Did you swap the 99 column? Or do you still have the 90?

 

Here's a nice little write up for the wiring.

 

http://comancheclub....-wiring-guides/

I've swapped over the 99 column. I'll take a look at the write-up, as well as what Eagle has suggested. Thanks!
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I've swapped over the 99 column. I'll take a look at the write-up, as well as what Eagle has suggested. Thanks!

 

Check the last post in the thread, Not sure if the 99 column is the same as the 95..

 

But their write for the brake lights only works with the 86~ column.

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Crap, you're right. Sorry. I used the XJ wiring and the MJ sockets. I had to replace the non weather tight connectors with weather safe ones. I got mine from painless. I also made new short harnesses from the tails to the XJ harness.

 

I tried to use the XJ sockets. I had mod the crap out of the light to get them in. It was easier to extend the wiring.

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Just a quick update. I was able to get things working properly along the lines of what Eagle posted. I ended up having to run on additional wire from the 99 XJ tail light connector back to the MJ tail lights. I made this wire the brake light wire and had to cut one wire on each MJ tail light for this to work. Now my top light is the brake, the middle is the turn signal, and the bottom is still the reverse light. I also incorporated a few other cool things, so I'll get a photo and post it soon.

 

Thanks again to all of your for your help!

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I've been thinking about this more and more from wanting to go HO on my '88. Couldn't one also use a trailer wiring adapter and use that for sending power to the taillights on the truck to keep things looking factory when the lights are working?

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  • 1 year later...

I'm in the middle of doing my rear brake lights and I'm having a hard time understanding which wires goes where. Does anyone have a diagram of the light harness from a 97 cherokee. I can't figure out which lines are for the tailights.

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  • 6 years later...
On 11/24/2012 at 4:12 PM, Eagle said:

I haven't done this swap, but I have given it a lot of thought because I think the XJ setup with separate brake and turn lamps (and 4-ways) is far superior to the MJ setup in which the 4-ways cancel the brake lights. I am considering changing mine to the XJ setup even without doing a newer-year conversion.

 

What I have in mind is to keep the MJ brake lights as taillights/brake lights. I would put amber bulbs in the backup light sockets and wire those separately as turn signals and 4-ways. And then I would add a pair of small fog lights wired to function as backup lights.

 

If you want to keep the stock backups as backups, the MJ has two stop/turn lamps on each side. It would be easy enough to split those, and run one lamp on each side as tail and brake lights, and the other lamp on each side as turns and 4-ways.

I keep reading about adding a wire to the comanche tail light harness to split up the running/brake lights but I don't know where to attach this wire on either end. Does it go to the brake light switch?

 

Should I just adapt all the xj wiring to the comanche tails? If so how do I run the passenger side through the body out to the tails?

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The XJ rear lights are all fed from the left side wiring bundle. The difference between the usual XJ setup, which has separate brakes and hazards, and the XJ Wagineer (which works like the MJ, with the brake lights and hazards sharing the same bulbs), is all at the rear of the vehicle. I thought I had posted scans of both XJ wiring diagrams here awhile ago, but I don't remember where or when.

 

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On 9/13/2020 at 12:09 AM, Eagle said:

The XJ rear lights are all fed from the left side wiring bundle. The difference between the usual XJ setup, which has separate brakes and hazards, and the XJ Wagineer (which works like the MJ, with the brake lights and hazards sharing the same bulbs), is all at the rear of the vehicle. I thought I had posted scans of both XJ wiring diagrams here awhile ago, but I don't remember where or when.

 

Left side meaning driver side?

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Well I got it done. Almost everything is ran through the oem mj harness. had to run an extra wire to make the pass side rear turn signal function properly. It is currently routed along the pass side frame rail but may extend the wires so it goes down the driver side frame rail with all the other wiring.

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  • 4 weeks later...
On 10/13/2020 at 8:02 PM, Swampy said:

Just saw this and yes I could do a DIY writeup of the whole 96 swap too if needed.

 

get on it! :L:  don't wait for someone to ask for it, get it out into the internet so people can find it for decades to come. :D  

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On 11/24/2012 at 12:35 PM, LoTGoD said:

I found a few threads here, however none of them had a finished walkthrough. I've completed 90% of my 99 XJ swap in to my 90 MJ. At this point the only electrical issue is the running/brake/turn lighting on the rear. As has been stated, the XJ wiring and socket types differ from the MJ. I've isolated the XJ wiring and MJ wiring. I have the running lights working properly. I can also get the turn signals to work properly. Where the problem comes in is when I hook the brake light in to the equation. The XJ setup uses different wires and bulbs, where the MJ setup is all intregrated. Has anyone sucessfully intregrated the XJ electrical through the OEM MJ rear wiring harness? Everything I know about electrical wiring tells me I know nothing at this point. I would appreciate any help on this as this is my last real hurdle toget the truck on the road. Did I miss an article or thread here about it? Thanks a bunch guys!

can I get any diagrams u used because I'm having a hell of a time I got a 95 harness a 98 dash and I'm putting it in a 89 mj. easiest way I was told was to strip the entire xj (95) and strip your entire mj. then put everything from your mj in the trash and put the guts of the xj in the mj. it's been a battle mostly because I'm picky and wanted a 97+ interior. other then that it's been time consuming but easy. 

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