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XJS Electrical... how to diagnose

On my 84 XJS, the circuit that includes the instrument panel and reverse lights keeps blowing it's fuse, although I can't seem to ever catch the exact moment it happens.... ie, I put a new fuse in and it may last a half hour or a few days before I notice that the instruments have stopped working again. I tried putting a new reverse switch on the shifter, but that didn't fix the problem, nor can I pinpoint the fuse blowing at the same time the shifter is used.

In retrospect, I have had a nagging electrical problem for many years with this car, in that it would run the battery down if it sat more than

2 or 3 days without being driven; I had it in the shop several times for this, and they removed the anti-theft system and disconnected the cigar lighter, among other things, but the problem persisted. I got tired of throwing money at the problem so I installed a battery disconnect switch to use whenever I knew I wouldn't be driving the car for awhile.

Now recently I have this problem with blowing the fuse, and, interestingly, the last time I parked the car it had a blown fuse again, and I forgot to shut off the battery disconnect switch; it sat several weeks, and the car started right up (no battery drain!)... so I'm thinking whatever is blowing the fuse may be the same problem as the battery drain problem (or may not, I suppose).

Anyone have any ideas on how I can track down this/these problem(s)?

Reply to
WayneC
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do you have a tow bar??? could be some bad wiring in the tow bar electrics.

Reply to
Neil

Check the junction of the wiring loom & the dash/ignition circuits ( 2 large plastic connection blocks) for corrosion. Had similar experience cost around £400 in towing fees & £300 to fix the mess the breakdown guy made of the wiring!

chris b (XJ40)

Reply to
Chris Booth

Jaguars are famous for electrical problems

I am not familiar with your particular model ( I have a 78) but to find the problem I would remove the fuse and connect a "sonalert" or any type of buzzer to the opposite of the supply side.

Then insert de fuse and move all harness and the accessories that are connected to that fuse. When the buzzer stops buzzing, you know you have found the problem

If you have more that one wire connected to the non supply side of the fuse, you could also insert individual fuses and this way get a better idea on the location of the problem,

You can also replace the fuse with a 12Volt bulb (high current) and move things around . When the brightness of the lamp changes you know where the problem is.

In any case, intermittent problems are hard to trouble shoot and in a Jaguar are certainly not an easy task.

Reply to
Vlad

No, no tow bar.

Reply to
WayneC

Interesting thought... but probably what I need is something that will start making noise when the power ceases (fuse blows) so I can figure out if something in particular is happening at the time it blows. Something like those old aftermarket buzzers that warn you when you've turned the ignition switch off but left the headlights on.

Another interesting thought.

Or maybe add a light to the circuit and put it on top of the dash.

Reply to
WayneC

That is what a Sonalert is. They use to cost about $5.00 but today you can get a buzzer 3 small batteries and a microswitc for a dollar . I know, I just purchased 4 of them at the local dollar store.

Reply to
Vlad

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