X350 Jaguar XJ6 - Major electrical problems
Discussion
Right, I'm at my wits end with this, so I'm really hoping somebody here can help me. I've tried asking on owners forums but haven't got anywhere, so I've turned to Pistonheads in my hour of need 
I've got a 2003 X350 shape Jaguar XJ6. Just over two months ago, it developed an electrical fault: when the headlights were turned on, the window switches would stop working, the clock/centre console illumination would turn off and the interior light would remain on very dimly. Without the headlights on, the windows etc worked fine.
I took it to a specialist who replaced some wiring going to the body processor unit, and the problem appeared to be fixed. However, it came back again only a week or so later. I ended up taking it back to them various times and they found that the problem was causing a fuse (either fuse 7 or 14, can't remember) in the drivers side fuse box to blow. They ended up replacing the 15 amp fuse with a 30 amp fuse, then replacing it again with a 15 amp fuse, which seemed to "blow" the short circuit and fix the problem.
That was about 5 weeks ago, and it was fine until a few days ago, when I was reversing into my drive and my father commented that when the brake was applied whilst I was reversing, one brake light would turn off, and one of the two reversing lights was very dim. Then, the next day, I was driving along at night with my lights on, went over a speed bump and the old problem came back again - the interior light came on dimly, windows stopped etc etc.
I phoned the garage I'd taken it to and they said it could be the body processor module, but they weren't sure. By now, the MOT had expired, so I took it down to my friend and left it with him to MOT.
I got a call from him this morning to tell me it had failed on the rear lights. I've asked him to check and replace any blown fuses, but if that doesn't work I don't know what to do. I've already checked the earths, bought a new battery (£100), and paid the garage for their work (£500) and I don't want to keep chucking money at it (likely to be well over £500 again for a new body processor parts+labour) when it may not even solve it. I'd be more than happy to spend another few hundred if I knew it'd fix it, but I don't want to keep spending money on fixes that don't work.
So, does anyone have any idea what my problem might be? Or do you know someone who might be able to help me out? I'm based in the south east and any help would be greatly appreciated.
Many thanks
I've got a 2003 X350 shape Jaguar XJ6. Just over two months ago, it developed an electrical fault: when the headlights were turned on, the window switches would stop working, the clock/centre console illumination would turn off and the interior light would remain on very dimly. Without the headlights on, the windows etc worked fine.
I took it to a specialist who replaced some wiring going to the body processor unit, and the problem appeared to be fixed. However, it came back again only a week or so later. I ended up taking it back to them various times and they found that the problem was causing a fuse (either fuse 7 or 14, can't remember) in the drivers side fuse box to blow. They ended up replacing the 15 amp fuse with a 30 amp fuse, then replacing it again with a 15 amp fuse, which seemed to "blow" the short circuit and fix the problem.
That was about 5 weeks ago, and it was fine until a few days ago, when I was reversing into my drive and my father commented that when the brake was applied whilst I was reversing, one brake light would turn off, and one of the two reversing lights was very dim. Then, the next day, I was driving along at night with my lights on, went over a speed bump and the old problem came back again - the interior light came on dimly, windows stopped etc etc.
I phoned the garage I'd taken it to and they said it could be the body processor module, but they weren't sure. By now, the MOT had expired, so I took it down to my friend and left it with him to MOT.
I got a call from him this morning to tell me it had failed on the rear lights. I've asked him to check and replace any blown fuses, but if that doesn't work I don't know what to do. I've already checked the earths, bought a new battery (£100), and paid the garage for their work (£500) and I don't want to keep chucking money at it (likely to be well over £500 again for a new body processor parts+labour) when it may not even solve it. I'd be more than happy to spend another few hundred if I knew it'd fix it, but I don't want to keep spending money on fixes that don't work.
So, does anyone have any idea what my problem might be? Or do you know someone who might be able to help me out? I'm based in the south east and any help would be greatly appreciated.
Many thanks
Sounds like an earthing fault to me.
Locate all the earth straps - I don't know where they are on the X350 - remove them and clean the contact areas. That may not solve your problem but you can't rule earthing faults out with symptoms like you describe until you absolutely know you've got clean low resistance connections to earth.
Locate all the earth straps - I don't know where they are on the X350 - remove them and clean the contact areas. That may not solve your problem but you can't rule earthing faults out with symptoms like you describe until you absolutely know you've got clean low resistance connections to earth.
Edited by Jaguar steve on Friday 10th January 15:56
Geekman said:
I've already checked the earths
There are dozens of Earth points on an X350 Jag , but the ones that are known to cause problems are the 3 earth studs in the engine bay. They are all attached to the front metal cross member under the plastic cover right at the front of the engine bay. If you havent already done it you need to remove the nut, slide off all connections, wirebrush then put them back using some kind of electricians contact compound (cant remember what its called) to ensure good contact in future. On my previous XJ they looked fine but the horn wasnt working and I had a lot of odd electrical gremlins, Turned out one of the earths had to much corrosion between the contacts that it wasnt connecting. It looked fine until I took it apart and found masses of corrosion between each of the contacts.
If you've already done this at least its eliminated from the equation.
I have also had weird gremlins when the CANBUS connections between modules was intermittent. Easy fix is just to unplug then reconnect the CANBUS network connector on any module thats playing up.
Thanks for the replies so far. Unsurprisingly, it failed the MOT, so it's now even more crucial I get this fixed. I have already taken apart the three studs in the engine bay, but I'll do it again and clean them more thoroughly. I've got the electrical diagram which I'm trying to make sense of, and not having a huge amount of success.
From what I've read so far, I'm thinking it may be something to do with the ground point of the passenger side rear light. I'm at a loss as to where that actually is though - it's not very clear from the diagram.
From what I've read so far, I'm thinking it may be something to do with the ground point of the passenger side rear light. I'm at a loss as to where that actually is though - it's not very clear from the diagram.
Page 17 of this document shows all the earth points, might help ?
http://www.captainjaguarscathouse.com/Electrical_G...
ETA: also shows the locations of every control module
ETA2: Im no expert but looking at that document on p50: exterior lighting rear, all lights link into the rear electronic module, this appears to use 3 earths, all appear to be connected to G24 which if facing the rear of the car is in the boot right side towards the front of the boot (see diagram p17). Probably not a bad idea to find all the earths in the boot and give them a good clean up anyway.
ETA3: If I was you I would find that control module and disconnect/reconnect every single output to make sure the connections are good. If I understand the diagram correctly power is fed to that module and all earthing is from that module. The lights dont have their own earth they are simply connected to the module outputs - its basically a big switch for all the lights. So you are not looking for an earth for the rear light clusters(s) , you are looking for the earth for that control unit. As its only affecting one light then I would suspect the output connector on the control unit which may just need to be pulled out, cleaned and reseated. Got to be worth a try.
http://www.captainjaguarscathouse.com/Electrical_G...
ETA: also shows the locations of every control module
ETA2: Im no expert but looking at that document on p50: exterior lighting rear, all lights link into the rear electronic module, this appears to use 3 earths, all appear to be connected to G24 which if facing the rear of the car is in the boot right side towards the front of the boot (see diagram p17). Probably not a bad idea to find all the earths in the boot and give them a good clean up anyway.
ETA3: If I was you I would find that control module and disconnect/reconnect every single output to make sure the connections are good. If I understand the diagram correctly power is fed to that module and all earthing is from that module. The lights dont have their own earth they are simply connected to the module outputs - its basically a big switch for all the lights. So you are not looking for an earth for the rear light clusters(s) , you are looking for the earth for that control unit. As its only affecting one light then I would suspect the output connector on the control unit which may just need to be pulled out, cleaned and reseated. Got to be worth a try.
Edited by Dodsy on Saturday 11th January 19:16
Edited by Dodsy on Saturday 11th January 19:21
Also strongly suggest you repost on this forum http://www.jaguarforum.co.uk/f32/
Lots of experts who will be able to help
Lots of experts who will be able to help
I had a very similar problem. Turning the lights on slowed the indicators, the side lights dimmed and all sorts of other queer electrical problems.
The earth post to one of the headlamps (they're HID) had nearly snapped off. A thin sliver of metal was all that held it together.
The earth post to one of the headlamps (they're HID) had nearly snapped off. A thin sliver of metal was all that held it together.
Edited by DouglasXK on Wednesday 15th January 17:09
Thankyou for those replies, much appreciated. I'm going to take the boot lining out tomorrow, and unplug/clean everything I can find. I've already checked the front studs, but I'll do so once again. Battery voltage is fine, as the battery is almost new and a high quality model. I shall update the thread tomorrow evening - if I can't fix it I've called a man who was recommended on these forums, and he's happy to look into it for me.
Geekman said:
Thankyou for those replies, much appreciated. I'm going to take the boot lining out tomorrow, and unplug/clean everything I can find. I've already checked the front studs, but I'll do so once again. Battery voltage is fine, as the battery is almost new and a high quality model. I shall update the thread tomorrow evening - if I can't fix it I've called a man who was recommended on these forums, and he's happy to look into it for me.
Whatever you do make sure the battery is disconnected for a while before you start unplugging connections and take special care and time around air bag systems. FFS don't ever, ever leave the keys in the ignition either whilst you are working on the car. Keep them in your pocket just in case you accidentally trigger the central locking with all the doors shut...
Right, yesterday we checked all the connections in the boot, cleaned all the earths etc, and today we took one more look at the front earth studs and had a bit of a disaster....
When tightening one of them up, my dad managed to snap one off. Yes, I'd already told him that you need to be very careful, but either he used a bit too much force or the stud was exceptionally weak.
Looking at it, it doesn't appear to be the cause of the problem, but I thought I'd post a picture of where we're at now anyway. So, does anyone know what we can do now? Is it worth drilling another hole and putting a new stud in, or should I attach these wires to the lower earth point?
When tightening one of them up, my dad managed to snap one off. Yes, I'd already told him that you need to be very careful, but either he used a bit too much force or the stud was exceptionally weak.
Looking at it, it doesn't appear to be the cause of the problem, but I thought I'd post a picture of where we're at now anyway. So, does anyone know what we can do now? Is it worth drilling another hole and putting a new stud in, or should I attach these wires to the lower earth point?
I have a xj350 2003 which I have owned from new she been totally trouble free till I could not open the windows with the lights on centre console lights out interior light on dim. The exact same fault as yours I have tried all the same fixes as you to avail. Let's hope someone finds the answer to this problem soon .kind regards billtheboat.
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