- XJ8 - XJR Forum -

"Dead" Boot Button/Lights/License Plate Lights

Brian Vogel
*

forum user since 2006-07-23

 

Hello All,

It's been a few months since I was here last and I'm returning to ask for help. I will give as thorough a background as I can in hopes this will help with an accurate diagnosis.

Several years ago now my boot/trunk illumination lights became wonky and then finally gave up the ghost. I am certain that this is not because the lamps themselves are bad. Before they completely went dead the lights would very occasionally come on when the trunk lid was about 50% of the way open then go out as it continued to raise further. I had presumed this was likely a short in one of the lines in the harness that had flexed one time too many. I had also presumed that the two lights were on the same electrical line - this does not appear to be true but instead there is a purple-white and red-yellow wire for each light in the harness.

Every once in a while my trunk button would misbehave, too, but this always had resolved itself.

This brings us to today. After cleaning out my trunk I decided the time had come to check out the wiring harness that runs between the main car body and the trunk via the right side trunk hinge. Took the cover off, snipped the various cable ties, and thought I'd end up with the lights coming on as I gently manipulated the wires a bit: they didn't. On top of it all now everything that is electrical that is on the trunk lid (and uses that harness) no longer functions: trunk lights, trunk open button, & license plate illumination lights.

The fact that all of these have gone dead at one time makes me very strongly suspect that we have an issue with lack of grounding here, but I don't know how the trunk is grounded to the chassis. It could be via a strap I haven't yet located that's come loose or it could be through one or more of the lines in the harness that have somehow developed shorts all at once (unlikely, I know, but. . .).

All suggestions regarding how to best troubleshoot this would be appreciated. The only thing that still works is the key in the keyhole on the trunk lid!

Brian



Brian Vogel
--
1999 XJ8L BRG - SAJHX6044XC865293
AKA "Bri the Tech Guy" http://britechguy.com

Steven Petry
Jaguar Association of Greater Indiana *

forum user since 2007-02-03

 

Hi Brian,

Nice to see you are still about. I really think you are on the right track. I think you should further scrutinize those wires, on and in front of the RH boot lid hinge. I know from experience those wires many times break INSIDE the insulation, and can be hard to spot. The wire looks intact, but is still broken. Grab the wires individually and take a section about 12-14 inches long, give the section a firm tug along its length. If the wire is solid, no harm done, if it's broken, the insulation will tear and you find the break. Check them all, I'll bet a few are broken.

Good luck!

S Petry
'95 XJR
'97 XK8 Conv.

Brian Vogel
*

forum user since 2006-07-23

 

Steven,

Thanks a bunch. The fact that everything went out after the only thing I had done was to unwrap the bundling tape to try to diagnose what had been "the boot lights issue" makes me think that I had a bunch of marginal wires and have just "unleashed" all of the things that had *juuuuust* been holding together by untying them.

I am wondering if it might be just as wise to start splicing in replacement sections all along the area where they had to flex, one wire at a time, and see what, if anything, comes back to life. I'd like to use something significantly more "robust" as the splice than the original wire so that I don't have to do this again.

Let me know if you think that is too radical an approach. I'll certainly try what you've suggested, but I'm afraid of possibly screwing up something else further.

Brian, who has been fighting several proverbial fires the past few days, this one being low on the list

Brian Vogel
--
1999 XJ8L BRG - SAJHX6044XC865293
AKA "Bri the Tech Guy" http://britechguy.com

Steven Petry
Jaguar Association of Greater Indiana *

forum user since 2007-02-03

 

Sure, you could just section all the wires, some folks do that. Just don't use TOO heavy a wire, that could be just as bad. I personally just repair the damaged wires with an unshielded butt connector and some heat shrink tubing. That makes for a less bulky repair in my book. Then I make sure the harness IS NOT wire tied to the hinge or gas strut anymore. That way the flexing portion is bigger and way less prone to breakage.

Cheers,

S Petry
'95 XJR
'97 XK8 Conv.

Brian Vogel
*

forum user since 2006-07-23

 

Now that the weekend is here and I've had a chance to pursue this I thought I'd report back, with photographic documentation.

I decided first to remove the boot lid cover on the inside so that I could trace the various wires through the loom and down to the hinge. It never hurts to have your wires documented for later adventures!!

Then I thought rather than sectioning the wires I really needed to dig in down where they had been flexing the most. Little did I know that this was, contrary to what I would have expected, about 3 inches inside the plastic harness bundle. Lesson to all: DON'T presume you can see the maximum flex point. Also, better to search for this *before* starting to take off cable ties, tape bundling, etc. Once the wires are unbundled it is much more difficult to ascertain where the whole harness had been flexing the most.

As luck, or at least diagnostic luck, would have it when I was tracing the wires for the two boot illumination lights one of the wires slid right out of the plastic harness bundle, completely severed. After I cut a bit of the tape wrapper back to expose the entire bundle by about 4 inches what appeared but four wires in precisely the same condition. One appears to be the common ground wire for the boot illumination lights, one the common 12V+ source for both license plate illumination lights, one the common ground for the license plate illumination lights, and one the ground wire for the electric boot release. See the attached pictures for shots from the boot lid side of the equation and the in-boot harness end as well.

This now leads to a question: Will it matter which of the two black wires I connect to the other two black wires? I suspect that both are simply ground wires for their respective functions, so I would presume it should not, but I could be wrong. If I am wrong, can someone guide me as to how I go about determining which black wire on the boot lid side should connect to which black wire on the in-boot harness side?


Brian Vogel
--
1999 XJ8L BRG - SAJHX6044XC865293
AKA "Bri the Tech Guy" http://britechguy.com


Brian Vogel
*

forum user since 2006-07-23

 

And now the photo from the boot lid side.

Brian Vogel
--
1999 XJ8L BRG - SAJHX6044XC865293
AKA "Bri the Tech Guy" http://britechguy.com


Steven Petry
Jaguar Association of Greater Indiana *

forum user since 2007-02-03

 

Brian,

You should be good to just splice the black wires together and not worry which went where. The only black wires going into the boot lid are grounds for the number plate lamps. They ultimately splice together to the circuit grounds for the side markers. All the other items in the lid that have ground circuits are black/white tracer colored wires.

Hook 'er up!

Cheers,


S Petry
'95 XJR
'97 XK8 Conv.

Brian Vogel
*

forum user since 2006-07-23

 

Steve,

Well, I didn't splice 'em together, but I also went with my gut and didn't worry which was which since in my experience solid black wires are virtually always grounds. I needed to get this job done within a day, and did.

Let me tell you the worst part was getting the boot lock screws that hold the actual boot lock along with its plastic cover back in place. I had to remove this to get decent access to the wires to trace them, and it was a real *%*#(%% getting those screws started again.

I've also attached a photo of the insulated butt connectors I picked up at Radio Shack to splice the wires back together. These were just perfect for the job, and I couldn't find anything nearly this small at any of my local auto parts stores.

Brian, who's now getting the inexplicable and intermittent "Stability Control Failure" and ABS light coming on again [with no rhyme or reason - sometimes just turning the car off and on again clears it.]

Brian Vogel
--
1999 XJ8L BRG - SAJHX6044XC865293
AKA "Bri the Tech Guy" http://britechguy.com