Ok so this post has grown from another post I had regarding inoperable transmission shifter. Root cause of that problem was the #7 5 amp fuse in the left heel board fuse block. I got some ideas from Boomer from Boston with no joy yet on finding problem.

I know this fuse along with 3 other go to the Body Processor Module behind the glove box.

Here's what I know:
- fuse blows without key in the ignition
- with fuse blown, trans shift interlock does not work
- no visor or overhead lighting, have read posts about wires shorting here, have pulled wires back to main overhead harness, dropped front end of headliner, and see no problems
- mirrors do not adjust with door buttons, but they do work on pre-sets
- steering wheel also moves up & down on pre-sets (never telescoped another known problem)
- glove box light does not work, investigated bulb it was good, even replaced still no light
- gas cap does lock & unlock (thought this might be on same circuit)
- remainder of dash lights work, must be a seperate circuit
- disconnected each front door harness seperately in an effort to isolate each door (mirrors), still no change fuse blows
- conducted quick visual look behind glove box and instrument panel while out, didn't see anything obvious

The fuse blows instantly. I'm a nuts and bolts Guy, but I assume that since the battery is not drained down that the problem is after the fuse block...? Yes?
I am going to get a line/cable tracer that Gus mentioned on related electrical post, and try following harness looking for problem. I do have the electrical manual and willl get out the magnifying glass and have a look if needed.
Does anyone have any ideas of common areas to look at? Until I try the cable tracer, I'm at a loss. Sorry so long & thanks in advance for any thoughts.

 

Fuse #7 is actually 15A, but that is the least of your problems!

I think you should start with the Body Processor Module wiring harness. Do you have the wiring diagrams for the XJ8? You can see the various functions that are controlled by fuse 7. It is a PITA to get the BCM out, but doing so is the key to doing more targeting troubleshooting.

Even though you have looked in the vicinity of the headliner wiring, the best way to eliminate that is to cut the wire feeding the headliner wiring, back at the BCM. (as described in my postings some time back). Could be a short that you can't easily see. If that doesn't help, you can one by one cut the other circuits coming out of the BCM, and try to replace the fuse. Sooner or later, cutting one of the wires will allow the fuse the be replaced without blowing.

I suppose it IS possible the BCM itself is faulty, but the consensus seems to be that the BCM is robust enough to very rarely fail.

 

Did you type the amp info incorrectly? 5 amp vs correct 15 amp. That obviously would be a problem.

So ......... since the fuse blows instantly you can not verify that any of the non functioning items are fixed with the fuse? Correct?

..........feel you pain -- can be very difficult to find this type of problem.


Have you changed any of the bulbs on the car? I did have a problem years ago with substandard bulbs - very strange. Also ..... a blown bulb can create a short - I have only had it happen once but.

I would pull every bulb powered by that fuse

 

The passenger side boot hinge has a bundle of wires in it. Remove the plastic cover and manipulate the bundle, hopefully stoping the short circuit. Then try a new fuse. That bundle has done that on both of my xjrs.

 

All: Yes it's a 15amp fuse, senior moment on more than one occasion last night.

Initial problem started when Son pulled car up on ramps to change the oil. Couldn't get it out of park afterwards, and the rest is history. I forgot to mention in original post, that the first time I replaced the fuse, it worked great for 4 days, then blew.

Boomer: Understand, looked at BCM, hoping to find something else first, but may have to go there anyway. And yes I do have the electrical diagrams. I'm not ignoring your advice. Keep it coming.

yeldogt: fuse did hold for 4 days, and to the best of my recollection, all above did work, with exception of telescoping steering column, which never did (another problem) No bulbs changed prior to problem starting. Have since changed out all dash bulbs while things were opened up for shifter replacement. Checked overhead bulbs they're ok, all are disconnected now(visors & ovhd console removed), effectively isolating them from equation....

john: I never would've thought the boot hinge harness would be tied to this. Should not surprise me though. This is on my long list as I have a couple of trunk issues, one license plate out (bulb is good), remote release is inoperable also. Hummmm....better move it up on the to do list. That's fixed the problem for this particular fuse...? Thanks

I'd like to find connection for the overhead harness wherever it may be and disconnect there to isolate. Suppose I'll get out the electrical diagrams. No room in garage, and still wet / cold here, so it may take a few days to update. Keep the ideas coming though. I'll try almost anything.

 

You Guy's never fail to save the day! A big THANKS to John for the trunk harness pointer. Boomer, I'm glad it wasn't the BPM, but, thank you for the insight. I got to looking at the wiring diagrams the other night and behold the trunk harness is tied into the cabin harness. So tonight I took a better look than in the past, removed all tape, etc. and found that five out of the ten wires were broke in two, with a couple fused together, source of my short no doubt. I separated all wires, hooked up battery, replaced bad fuse and everything up front that wasn't working is now working. After I splice the wires back together, there's no doubt that the few things in the trunk that didn't work will be working also. I can't express how helpful everyone at this forum has been. It's a pleasure logging on here to learn, and help others myself when possible. It's going to be a good weekend!

 

I have to agree, in that the combination of this forum and Ebay for used parts at a reasonable price has made it so that I can both own and drive jaguars. I have owned a jaguar for many years, but found that before both the forum and Ebay I had a driveway ornament. I don't believe they are less reliable than other cars, just more expensive to fix, and harder to finde parts for. I still buy parts from the dealer for some things, but have found the internet is a great source for used parts.

 

I love a happy ending, good job to all the advisers to this particular thread, you get a gold star! ok, well its a little trophy, no stars in our smiley table

 

The question might still be what caused the wires here to fuse, beyond the to much current.
I had a similar problem, and the source was the trunk lights had been banged up in the lining and were intermittently shorting causing the fuses to blow.
May not be your cause, but unless it was mechanically damaged, something causing fusing of wires still exists.

 

dsetter: To expound upon my findings. The five wires that had broken/parted, did so at the same location in the harness. Immediately where the harness exits the back side (fwd in car) of the plastic hinge cover inside the trunk, where there is a bending point where the harness becomes unsupported and heads forward past gas tank. Some of these wires are hot all the time, I would expect the trunk lights, the button switch for openeing the trunk, and possibly others. The trunk light wire had fused to another (presumably) hot wire when they came into contact with each other at the break point. I was so happy to find a problem, that I do not remember the color of the other wire. I have spliced all wires back together, and evertything is working with the exception of the trunk lights. I removed the bulb holders, and checked bulbs, for these lights while still plugged into harness and still does not work. At this point, I don't believe it to be the harness as I had nearly all of it exposed, and retaped during this evolution. I'm off to search some threads regarding the trunk lights specifically. I think I remember reading about a switch of some type (such as the old mercury switches that used to be used for trunk and engine hood lights in the old days) that may be playing with me now. Though all I see right now is a couple of connectors.

 

I didn't find a more recent thread than this one regarding my problem. I was hoping if anyone had experienced this issue since 2011 and could provide some input, that they would do so.

My #7 left heel board fuse blew a few days ago disabling the side mirror, steering column, overhead lights/garage door opener and most disturbingly the shifter interlock. I put in a new fuse and today it blew again when I went to leave church. This time however, whenever i put in a new fuse it blows instantly. I had to override the shift lock to get the car home.

I am going to start checking wiring when i get home from work. Any additional tips that are not offered in this thread would be appreciated.

 

Well... Have you checked the trunk hinge harness like the OP posted? It is a well known problem!

 

Hey. Yes, I examined the wiring bundles in the trunk. Not a very impressive engineering display, in my humble opinion. That said though, none of the wires appeared to be frayed, bare or otherwise compromised. I guess it would be wise to do a more extensive examination as the OP also thought everything looked fine upon first inspection. There is a long tightly wrapped section running at the top to a connector just above the fuel tank. I guess I could unwrap all of that and check it?

I had the headliner replaced about 3 months ago, but I would think if they damaged any wiring it would have manifested itself before now. The wiring in the overhead console (the part I can get to and see) looks good.

I have done lots of repairs and upgrades to this car, all with a great deal of enthusiasm and joy. This issue however is more of a frustrating annoyance. My 25 year old BMW saves the day again and gets me to work.

I guess I need to remove the BCM? and do a thorough diagnosis. I will look for some directions on how to access that module.

Thanks for a place to think out loud.

 

Well, you say the same circuits are loosing power, the same fuse is blowing, and the trunk wiring is a well known problem, so it really seems you shopuld look there.

As to reliability, you could get a Honda to drive Some of us here would not be caught dead driving a Bimmer.

 

Hmmm, not so sure: 325i convertible was pretty cool (if it was a five speed). I actually wish I had hung on to my 88 325is. Owned 7 BMWs (first was a 69 2002), but none since I sold the Z4 in 07; and eight JLRs -- which I prefer. I am thinking of going back to Range Rover if this blasted ac can't get fixed.

Besides the bundled wires at the boot hinge loom, check for water in the module under the battery.

 

Jim:
I have a MY 03 Disco and it runs pretty good most of the time. In the 50,000 miles in 5 years that I have owned it, my longest time between engine lights is about 8 months

 

I have unraveled the passenger trunk hinge wiring bundle all the way to the point it goes into the taillight assembly; everything looks fine. After manipulating the wiring I tried another fuse, popped immediately.

I removed the glove box assembly to get a visual on the BPM. It's difficult for me to surmise much but the visible wires appear fine. I'm not sure how I would isolate various systems from here to localize the short.

With regard to the BMW, I'm not much on brand but I like the cars that I like. Growing up in NC there's always been "Ford verses Chevy" for trucks with die hards on either side. I've owned both, liked them both just fine. That E30 is solidly built and dead reliable; not to mention fun to drive. It's been the car I can count on for for almost a decade while various cars I've owned (Honda, Acura, Volvo, Chevrolet, Jeep etc) have come and gone. That said, I do love our Jaguars. My BMW acquaintances have a similar "nose up" attitude towards my Jags, I think it's funny.

Ok, back on topic. Sorry. I can't express how much I appreciate anyone who takes their time to help me. In fact, if you guide me to a victory in this repair you may disparage any car I own in the process! (leave my mom and wife out of it though).

 

First of all, it's unlikely anyone would have been able to assist me because this was a very obscure issue. Second of all I can't blame Jaguar in any way since this issue was NOT caused by Jaguar engineers (except that the car has an intricate and complicated electrical system, which is typical of top tier luxury cars).

I thought of the ONLY repair since I bought the car that I did not personally conduct. That was the headliner. I pulled down the drivers sun visor and found that the wire to the vanity mirror had been jammed into the bracket holding the visor, and that moving of the visor had frayed both of the wires. I unplugged the mirror light and tried putting a fuse in the number 8 slot again. No problem whatsoever. So I wrapped both wires in electrical tape and pushed the connector far enough into the headliner so that the wire was clear of the bracket and put it all back together.

So far so good.

 

Glad you found it! And thanks for the report back.

 

Amen, Ross. The way we learn is from those taking the time to report fixes that work.