1998 XJ9 VdP.

1. License plate lights. The lights above the license plates suddendy went out. Oddly, this is intermittent - they have come back on now and again (and only when I close the trunk....is this normal?). I read that breaks in the wiring harness/loom in the trunk can cause this. I traced (in an albeit cursory way first pass) from lights to where the harness leaves the trunk and no clear breaks in the wire are seen. I have a hard time believing both license plate bulbs blew. Anyone know which fuse in the trunk is for these license plate lights? Any other thoughts?

2. Trunk courtesy lights. They have a mind of their own - will come on and off at will. When on, I have jiggled every wire from the lights to the exiting of the wiring harness from the trunk and they won't go off. Yet, when I close the trunk and open again, they many be on or off.

Anyone faced similar gremlins from these two lights? Battery is new this year.

Many thanks.

 

My memory is that the switch is in the lock - so you could have a sticking switch ........ but I bet you will find that you have an internal wire problem -- they can be very hard to find and best to just replace the wires.

Also check to make sure all grounds are in good order.

 

If I recall, wires leading to the trunk lid, along one of the hinge bows, are prone to chafing and/or breaking through fatigue bending INSIDE the insulation. The fact that your issue was intermittent and showing up when you'd close the trunk may point in this direction.

Find the correct color codes for the wires in question and follow them more carefully from the light all the way back to where they would bend when opening/closing the trunk and you my find where an internal break has occurred.

Using a pin to pierce the insulation, you can measure with a voltmeter (or ohm meter if the case demands) both before and after the hinge bends to see if a particular wire has continuity or is broken at the bend.

 

Symptoms definitely match cracked wiring in the loom at the hinge. take the insulation off the loom to inspect it. I had exactly the same problem and on first glance everything looked ok, but when I started to peel off the loom insulation, I found multiple cracked wires. Once you have fixed the wires, I didn't reattach the loom as firmly to the trunk lid as it had been, which gave it a bit more room to move and will hopefully mean less strain on the wires in future.

 

That's a great thought--as I was playing with it, leaving the trunk half-open and closed, the license plate lights just came back on briefly but after a few times and opening and closing, went out again...any idea how I can get to that lock to see if it's sticking? That may be the answer.

 

Well ..... I don't think the trunk switch can have any effect on the license plate lamps ........ That is why I said you should check the ground ........ especially if you can have both the license lamps and the trunk lamps flicker at the same moment.

Otherwise --you may have a common ground wire to those lamps that is failing - I don't have the wire diagram in front of me.

The wires to the trunk are thin and it is a common problem to have them break -- before I started playing with the lock I would invest $5 in a Harbor Freight multi-tester and give the wires a test

 

Hi, Exactly the same problem on my XJ8, number plate lights on and off when the boot lid was opened and closed. Found to be, as others have said, broken wire where the loom passes through the right hand boot hinge. The colour wire I seem to recollect was mauve/white. At first glance all seemed OK until I peeled back the insulation. When I pulled on that wire it just came apart. Found several other wires with cracked insulation as well. Soldered the broken wire and taped up the others, everything fine.

 

Does anyone have a wire diagram or maybe explain what the ground wires look like?

I went through all wires from trunk/boot origin to the loom on the right hinge of the trunk/boot, and there were no breaks. HOWEVER, just underneath the hinge before the wires become wrapped by the thick black plastic loom, there were a few kinks, with a clean beak in the mauve/white wire coming from the license plate lights which I repaired - immediately the license plate lights came on. I was delighted. Easy fix. I closed the trunk and they went out again and stayed out...I cannot find any clear breaks in any wire and the one I repaired is fine (I even took it apart and repaired it again. No luck). There was a similar break in a wire to the trunk lights which I repaired. I hate intermittent faults.

Now, I can open and close the boot..sometimes the trunk lights are on and sometimes off. The license plate lights never came on again after that first fix. This concerns me as I don't want a ticket. Multiple breaks inside the wire or a common ground issue? I'm scared to probe too deeply and damage the wire to the trunk lock, and I am also concerned that the wire to the license plate lights may be damaged as the loom dives deep in the trunk or further forward in the cabin.

I am at a loss. Any suggstions? My car never has easy 'common problems' for the '98 XJ8. Thanks in advance.

 

I took another look today. The break in the mauve/white wire (one seems to come from each license plate light) seems insurmountable (I cannot get that wire to work PAST the break but the wire is fine PROXIMAL to the break. I can hook up the broken end (linked to one license plate light), and by piercing the second mauve/white wire to the other license plate light with a safety pin, the circuit is complete and both lights are on (but of course it links straight to the battery and will stay on all the time regardless of whether the tail lights are on!). This verifies the lights, and the broken long wire coming from license plate light is fine up until it passes the trunk hinge.

What it going on? It seems that the segment of broken wire PAST the break (where it dives into the trunk) is either bad, or there is an issue with the fuse or ground.

Please help. Does anyone have 1) a wire diagram for the trunk lights, 2) a location of the fuse for the license plate lights 3) any ideas what is going on. This should be a simple fix.

Thanks!

1998 XJ8 VdP.
-----
Edit: I got impatient and don't want a ticket - I tapped into the tail lights. When they are on, the license plate lights are now on. Thanks to whomever suggested it.