Hi all, I have a 91 xjsv12 and i store it most of the year, I remove the battery and when I want to start it I just take it up and install it. Last month I went to do that and when I hooked up the battery I had to reset the alarm and when I went to start it I got a click then lost power to everything lights, dash, locks, no power anywhere. After I unhooked the battery and hooked it back up we had power again. Reset the alarm and turned the key and no power. Today I took a new battery up and got the same results, a click under the hood and all power shut off. Any Idea's on what this could be?

 

To lose all power that way, it would seem that the battery is losing connections. Either at the battery, or at the ground near the battery. Could even be losing connection at the positive side. Check your connections, let us know.

 

I suspect the ignition switch went bad. There is a rotary switch inside the steering column, sometimes the contacts go bad. Mine was exactly the same symptom, I disassembled the switch and cleaned up the contacts. Might be worth checking it.

 

Japthug, out of curiosity, did the car lose all power until you rectified it, or just when you turned the switch to the start position?

 

I am sorry, I should have read precisely. In the case I stated power locks can't die.
It must be the battery harness problem.

 

Thanks for the replies, I understand the more info I give the easier it will be to fix this. one of the things that are confusing me is when I turn the key to the first position I have full power i can run the fan the stereo the lights etc when i go to position 2 there is a click under the hood then nothing but the real confusing part is sometimes i have to unhook the negative and reconnect it 3 or 4 times before i get the alarm buzz to resume and the power to come back

 

I was thinking this was an alarm issue caused by my taking the battery in and out so often (if i left battery in it would be to low to start the car after 2 weeks) but I wouldn't think the alarm would shut off all power. It actually acts like when you are putting a battery in and you don't have a tight connection at the battery and you turn the key it more or less shorts out the battery until you get it tight enough. I called my local Jag mechanic and he seemed to think it was a loose connection on the starter but the click I hear is on the passenger side top of engine? I am thinking I have a loose connection somewhere?

 

Losing power totally keeps me thinking you have a bad main ground or power connection problem. It will most likely be in the rear. I think that most of us gearheads have suffered this same malady with other cars. Its just that the battery being in the rear, and the complex looking nature of these cars make us think the worst. I'm also wondering if you have installed a non-vented battery at some point. The acid fumes can really wreak havoc in the trunk.

 

by non vented do you mean a maintenance free battery? I'm sorry if I seem ignorant on this subject but I only have known motorcycles and jet ski's that had vented batteries?

 

supercharged I agree with you on the connection theory i'm just confused on the click under the hood? you wouldn't by any chance happen to know where the negative is grounded on this vehicle? one other bit of info for you, the battery I took up last month to start the car with was a rv/marine starting battery as i hadn't picked up the new battery for the car yet and when i tried starting it I did get a slow crank on it at first then I had the issue with all the power shutting off (the rv battery was 650 cca it is used just for stsrting a boat then I have a deep cycle for everything else)

 

I think the click sound coming from under the hood is a starter or a AC compressor clutch.
What do you mean by resetting the alarm? If the car is equipped with an aftermarket security system it might be the reason.

 

Japthug, it is the factory alarm, when you first hook up the battery it makes a tone every five seconds or so and the security light on column stays lit, by pressing the button on the fob a few times the tone goes away and the security light flashes, then you can set the security system to lock or unlock, as for the click as soon as it clicks all power dissapears

 

Thank you for the info, I didn't know about the factory alarm, none of the XJSs in Japan has that.

So it would crank but died... how about a bad starter?
If the starter motor line shorts, large current drains and everything can be dead.

 

japthug, the jaguar security systems are sometimes a nightmare, my 2003 x-type is in the garage at the moment because with the x-type there are 7 system modules that need to talk with each other in order for the car to start, the fuel pump went bad and we replaced that but when my mechanic was buttoning everything back up he had found a wire that wasn't connected to anything (previous owner had installed an aftermarket stereo which is a no-no in these cars) so he pulled the wire out and that was it for starting it. The security system shut off the car. I had it towed to north coast exotics in Cleveland ohio owners name is Earl (fantastic jag man) He proceeded to cut a new key, replace some of the modules and was still having trouble with it he ended up almost dismantling the entire electrical system until he found where the stereo shop had tied in to everything and he used a donor x-type to get all the harnesses and components back to factory. He then had a problem with the throttle body sensor flooding out the engine, which in turn put it into limp mode, again this was a wiring issue and he finally has it all sorted out and it's running fine now ( i know long story but the basis for all the trouble was the security system) Earl told me he couldn't charge me for all the time he had in that car because it exceeded the value of it! But he took it on as a challenge and with everything he replaced it was a 900 bill So I was very happy. (side note, when he got it to start there was no radio, no climate control and the dash would not work but he has them all working great now. all from a stereo system)
I'm going to take supercharged advice and start running back the connections from the battery to see if I can locate the issue. The starter is above the cat. converter so I'm hoping I find it elsewhere first!

 

If you pull the carpeted covers off of the inside of the trunk, nearest the battery, you will see the first big connection. The ground wire of the battery goes directly to it.

The orginal battery of a XJS had a vent tube, that had a vent line directly venting the battery under the car. A marine battery may be maintanance free, yet may still emit fumes without this venting tube. I use one of the gel batteries in my car, as I read where one guy had his entire trunk become corroded from using a vented battery in his trunk without venting it.

The main wire of the positive side goes all the way to a main post on the firewall, above the starter. This same post feeds all other areas of the car, i.e. fuse panel, starter, etc.

My thoughts are that the ground near the battery is losing connection.
I just chased down a perplexing problem on my car. The fuse for the windshield wipers had power until I turned on the wipers. As soon as I did, I would lose power to the fuse. I tell you this, because I started from the wiper motor, working my way back to the wiper switch, finally to the fuse panel. The spade connector had become corroded from a leaking winshield?, and the corrosion allowed power to be there, until I needed amps. I feel this is exactly what is happening to you. You have power, until you need amps to turn the starter, which causes the loss of all power. Put a new battery in, and the slight movement causes you to have power, until you require amps. (If that makes sense).