Electrical issue - Jaguar XK 2005 (pre production model)

[Karlos]

Hello,

Can anyone help me, please?

I have an electrical issue with my Jaguar XK 4.2 V8.

Long story short, I started to experience some electrical gremlins but wasn't overly worried. One afternoon, when returning to the car, it wouldn’t start, the lights were flashing, and the key got locked in the insert. I tried to jump-start the car, but I think I did this wrong. The RAC came and said I had blown my 400-amp mega fuse, probably trying to jump-start it, but I don't think this was the original problem. The car has since been towed and the fuse replaced, but I am still experiencing some electrical issues with the car not being able to start unless the battery is disconnected and reconnected several times. After the incidents and watching a YouTuber "Life on Cars," I recently checked and had to splice the earth cable under the drivers wheel arch.

The RAC man and the garage said there's nothing wrong with the battery, but when I put a multimeter on it, it read 11.88V. Does this warrant a new battery?

I would be grateful for any help.