Hi everyone. To sum up an aggravating situation, the battery in my 2004 XJ8 is stone cold dead and the trunk won't open. (And it won't take a charge via the cigarette lighter since it's too dead for that to help.)

I've tried the key in the hidden recess under the lid, and it inserts and turns freely, but no luck. The mechanic at the local Jag dealer swears that if I spray penetrating oil inside the key aperture under the lid and let it sit for 24 hours, the key will definitely unlock the trunk - the theory being that the tumblers are stuck and need to be freed with the oil, despite the ease with which the key moves. So I have 23 hours and 14 minutes to go.

But I've read that if a booster or battery is connected to the positive battery terminal in the fuse box (with the negative connected to a nut or bolt somewhere) that should deliver sufficient amperage to at least get the electronic trunk release to work. (Which would allow me to install a new battery.)

Frankly, this option scares me a bit since I'm not sure where that terminal is.

I am attaching a photo of the fuse box. Can anyone give me some guidance? Many thanks.

 

I take it you tried leaning down on the boot lid as hard as you could when you tried to open the manual lock ? It takes the stress off the lock and allows it to move more easily

 

Well, no, actually. I'll give that a try.

 

Patrick, you are a genius! I owe you a scotch the next time I'm in Gloucestershire. And we can talk about physics!

 

Yep, that lock gets really tight through, well, never being used, actually. I was about to give up for fear of breaking something, when it suddenly occured to me ... and bingo.

Cheers ol' son.

 

I had the same problem with my old x308, the lock had never been used, and the key would barely go in let alone turn, I used a can of WD40 with a plastic tube on it, left it for a bit then worked the key in and eventually it freed off and worked fine, so on every service i lube the lock, and make sure it still turned. The minute I got my X350 home, I went straight to the back to check the manual lock worked, It did and just to be safe I sprayed some white grease inside and worked the key a few times to get it around.

As for the positive terminal in the fuse box, all you really needed was to get enough power into the cars electrics to be able to pop the trunk, looking at the photo, I would have put one lead to earth, and got someone at the rear ready to pop the trunk and touched a positive lead to one of the posts on the 80amp fuse in the top of the photo, don't try to start the car doing that, but it will power the electrics enough to open the trunk. You could probably connect a trickle charger that way too, but if the trunk opens, then that doesn't need to.

 

As a general rule putting any form of liquid lubricant, other than things that evaporate quickly and completely, is not a good idea; the surface tension and 'stickiness' can play havoc with the small and light tumblers in a lock.

The best thing for stuck locks is to minimise the load on them (lean down on the boot lid), and if necessary and if possible subject them to fairly hard and rapid vibration.

The only lubricant you should use on a lock is something like graphite; eg rubbing the key with a 6B pencil. You used to be able to buy small packets of graphite powder to use on Yale (UK make of lock) type door locks.