GeneXJ

This is a post about fixing that pesky license plate light, as well as other issues you may encounter due to broken wires at door and tailgate hinge points

I recently got pulled over for having my license plate light out. I thought it was a simple bulb fix. But like with most issues with the Jeep, I was very wrong. After replacing the bulb and checking the fuses, all to no avail, I finally found a few probable causes while searching the forums, but there was no concrete answer.

I decided to write this thread to point out a the most probable issue for these weird types of electrical issues - broken wires in the harness at vehicle to door pass-through points. These seem to be the common causes for plate light issues in the tailgate as well as speakers not working in the drivers side doors. I am sure there are others, depending on which wires are broken.

Basically any malfunctioning equipment on the doors and the tailgate can suffer from the broken wire issue - from power locks to speakers not working, so before you go around replacing your switches, check your wiring harnesses at the door and tailgate hinge areas for any broken wires.

The most important thing is that if you have an old XJ, you probably have some broken wires are the door and tailgate hinge points. So when trouble shooting related components, check those points first.

Diagnosing and Fixing the license plate light issue:

Your license plate light and third stop light do not have an individual fuse. If your rear tail lights and indicators work and your plate light and/or third stop light don't, then its either a bulb or a wiring issue, and the bulb is the one that most of use rule out first, to our dismay.

Instead of fiddling around with a multimeter trying to trace which wires are broken - which is very time consuming and unrewarding, I jumped right in pulled out the wiring harness from the tailgate, and cut open the sheath. Sure enough, most of the wires there were broken.

Here is the view of the tailgate with the wiring harness pulled down. The part in the center of the pic usually resides in the tail gate hinge area, between the vehicle body and the tailgate.




Looking closer - all those wires are broken! There were 7 broken wires here, including the fat ground wires. No wonder my plate light and third brake light did not work, and my rear defroster and wiper kept blowing a fuse whenever I turned them on




This is a fairly painstaking, but still relatively quick and straightforward problem to fix.

1. Undo the screws that hold your plastic tailgate paneling, along with the inner plastic tailgate handle handle - located on the interior of the tailgate.
2. Gently yank on the the panel to remove it (it is held in place by plastic rivets that come off easily. Pull straight our from the tailgate body without tilting or twisting the panel, otherwise you might brake some of the rivets. No big deal if you do though).
3. Remove the 4 screws holding the thin plastic panel at the top of the tailgate on the jeep main body itself. This should expose the wiring harness.
4. Unscrew the two bolts holding the tailgate wiring harness connector in place to free up the connector. Pull it out a few inches towards yourself and carefully disconnect the 3 harness connectors.
5. Now your harness is almost free to move. You just need to remove the two, or single rubber grommet through which the harness passes. I cut mine in half longitudonally because it saves alot of time over haivng to pry it. It also works just as well when you put it back on, and makes everything much more accessible.
6. Next you need to pull the harness down to make the broken wires accessible to you. You may not see the broken wires yet, but you will.
7. Pull the harness down into the body of the vehicle several inches. Then take a knife and gently cut the nylon sheath holding the harness together at the location on the harness that used to be at the hinge. Peel the harness back a bit and you should see a few broken wires.
8. If a wire is about to break - its insulation is missing and its hanging on by a thread, it is better to just cut it, trim the ends, and resolder it. Now you are ready yo finally start fixing the issue.
9. All the wires are different colors, so it is easy to match up the correct pairs of broken ones.

To fix, the wires, all you need to do is solder them back together.

1. First you cut off the jagged ends.
2. Then you trim off about 1/4 - 1/2 inch of insulation from each end.
3. Don't forget to slide on shrinkwrap, if using that.
4. Twist the wires together temporarily.
5. Heat up the junction point with a soldering iron and add some solder to it. (Radioshack actually has a battery powered soldering iron if you are working outside).
6. Wrap up the exposed wires with electrical tape, or shrink your shrink wrap.
7. Make sure you add an extra bit of insulation to the ground wires, since all the wires are going to be rubbing against each other
   
8. When you are done soldering, the new connection points will be more rigid (due to the solder, and fatter (due to liberal use of electrical tape)

Be careful to position these connections at a place where they will not be constantly bent. You may need to move them away from their original location a few inches by pulling out the harness or pushing it into the vehicle or tailgate. I like to cut away the wiring harness sheath a bit and let the wires move more freely in regards to one another. That way, if one wire is shorter, it is not constantly stressed, having to move with the entire harness when you open a door or tailgate.

That's pretty much it. I know I skimped out on some details and pics on actually implementing the fix, but its pretty straight forward, and you can find plenty of info about how solder wires and wrangle a wiring harness.

If the speakers in your front doors or your power locks don't work, this could be a similar issue. Look for a rubber boot on the bottom half of where the door meets the fender to access that wiring harness and check those wires.

I hope this helps someone having this kind of. If not, ask me and I will do my best to help.

cpttuna

or you could run a wire to the left marker light and power the license plate light from there

GeneXJ

Yeah, you could definitely do that. That was my back-up plan if I could not figure out where the wires were broken. But running new wires is pretty much the same effort as soldering old ones, unless.. they're all broken as was the case.

Doing it this way though allowed me to also fix the third stop light, the rear window defroster, and the rear wiper, which is nice.

CCKen

Nice write up GeneXJ.

Waynerd

Good writeup. My symptoms were fuse blowing when I would use power locks as the wires to the lock on the hatch were shorting. Then the defroster stopped working. When I took it apart there were several other wires ready to break. What I did was cut the wires about 2 inches from the connector. Pulled them through the rubber boot and then cut them back a bit from where they pass through the body. I then fished new wires through the boot. Then spliced on the connector and then spliced wires in the inner area. Did this so the connections weren't in the boot. Just new wires passing through it. Also a bit more time consuming.

wizardpc

See Also:

In the first few months of buying this XJ, I had to repair the third brake light, washer pump, and door lock wiring. The defrost is gone now, and there is some funkiness with the wiper motor now, too.

I've grabbed another harness from the junkyard and will just be making a whole new one.