Hi Guys,
Got the above car with no power to anything. Got in it the last night to start it and had the display was on for a brief second and then nothing. No accessory power or anything anywhere now. Charged it up overnight and still nothing. My battery is pretty new and I keep it on trickle charge normally. My top is down and it appears that I cant get the vertical storage cover out of the way to see if I can pull the battery with the top down. Not sure how to get the top up and out of the compartment since the back lid doesnt want to come up manually for some reason. I know how to reset the top manually if it gets stuck in a position but the manual doesnt tell you how to open the convertiible top when it is closed. I am near 100% sure the battery is at full charge and lugs are tight though. An electrical diagram would be great. I have downloaded a pdf file service manual but i have seen a good diagram or trouble-shooting chart to follow. Any help would be appreciated.

Thanks!

 

As an additional note, I do have an electrical diagram as it turns out. I see there is a battery juntion box that has 2 (175) amp fuses and a (400) amp fuse for jump starting. Not sure where those fuses are as I dont see them on either the fuse box inbetween the rear seat and under the hood. I'll locate and figure that out though

 

That's not good!
Was the car starting/running OK previously? Still could be a battery problem. I installed a brand new battery last Summer that I did initial top off charge with a trickle charger before installation. Two weeks later, no start, no lights or anything. Charged again with a 15 amp charger and have had no problems since.

What is the battery voltage at the battery posts after you charged it? Charge with a real battery charger and not just a battery maintainer.

Maybe try a jump start from another car. Use the post in the trunk left side cubby (or its reciprocal under the left rear fender) for the positive connection and a nearby chassis ground for the negative connection if you can't get to the battery.

Are the major ground connections good? Attached is electrical ground diagram with general locations of all the connections in the car. "G" points are grounds

 

Also, the key fob is not being recognized as no functions work on the unit. I am thinking this is a power / fuse failure or a key fob issue. This is a crazy / electrical problem prone vehicle in my short year of owning it. But it is cool looking I'll give it that. The vehicle worked absolutely fine a few days prior.

 

Did you try another fob or change the battery in the current one? Or install the fob in the center console slot.
Still sounds like a car battery or ground problem to me.

 

Thanks for the reference diagram. That is a great help! I will try charging with a normal charger if I can get to the battery. That's my issue now as I cant even get to it with the top down and the vertical luggage tray not wanting to come out due to the top being down. I tried a new battery in the FOB and trying to start the car with the FOB in the console, no luck. Battery is my guess at this point as well. I'll check the grounds also. Thanks and I'll let you know how I progress.

 

You don’t need to get directly to the battery posts to connect the charger.
Use the remote positive post either in the trunk or in the left rear wheel well. this connects to the battery positive post.
Info is in the driver’s manual.

 

Didnt think about that. Let me try jump starting it. Thanks!

 

Battery needs a proper capacity test to see if it's capable of cranking the engine. Also becoming more common to have faulty earths and of course check fuses, though I've not heard of many of those failing.

 

Thanks! - When I get it going, I’ll pull the battery and have it tested.

Mark

 

This is messed up. Had it on a charger at 10 amps charge for 5 hours and it is not charging off the post in the trunk. Had it grounded underneath to the frame. Im going to try overnight off the connnected trickle charger leads to the battery and see what I got in the morning. I need to find out how to get this top up I think to pull this battery. Any help on this would be great appreciated.

 

You said you couldn’t open the tonneau cover.
There is a pull cable behind the right hand slotted cover in the trunk (opposite the cover hiding the charging post). That cable will release the tonneau cover. You’ll also need to release the hydraulic pressure, at the pump behind that same cover, to manually raise the top. See the owner’s manual for details on the steps to follow.

 

I only think that charger comes in handy if you not gone be driving your Jag for a very long time.I don't think it's healthy at all for the car to keep putting the thing on a charger daily if you drive it more than once or twice a week.Seems like it got to the point where it starts frying the electronics or fuses in the car.I think the computer modules in the XK are too outdated for it to figure out what it should be doing with the extra charges from the charger if the battery is already over full charge.I say use a volt meter to check your fuses 1st.The security module can go bad and cause the whole car to lose power and go into a safe mode and that's what happened to mine 1 time when the whole fuse box went bad from water leaking thru the convertible top into my back seat where the fuse box is.You said u have a convertible,so im guessing the same thing probably happened to you too with water leaking thru your top into the back seat on the fuse box without you knowing it.Could be the whole fuse box blown and gone bad and they less than $100 to replace if u get 1 used and u can put it in yourself by unscrewing 2 bolts and taking all the wires loose and placing them all back in the same spot of where they suppose to go on the replacement 1

 

Thanks guys! I forgot about the pull cable. I know the procedure now to get the lid and top up and out of the way.
I’m gonna pull the battery this morning. I had it on a trickle charger all night and did absolutely nothing. Still no power - battery is not charging. I keep my car in the garage and with a cover over it so there was no issue with water. But somethings fried - my battery I suppose at minimum. I’m going to get it out and I haven’t tested. Thanks for the help again and I’ll let you know how it goes.

Mark

 

Another update and it’s not a good sign. Took the battery out and it is charging up fine. I’m going to go get it tested but I fear a short somewhere else since it would not charge hooked up. Or a ground problem as someone mentioned prior. Other than checking fuses, which if blown would not normally be the cause of the battery not charging since it’s already now blown and would be an open circuit so I will have to think how to find the source of the short. Any advice Is appreciated.

Mark

 

One last up date for a few days. Tried a different battery and the accessories powered up. Only faults on the display was "back boot open" since I had a spare battery hooked up with cables on the ground and had that darn "hood latch open" fault that I need to take care of, but everything seemed normal until hitting the start button and everything goes black.
Maybe this battery which is just a regular sized battery doesn't have enough power, not sure. I can hit the start to turn on the accessories and try again with the same result. So we will see when first test and put in the original battery again (if it tests out OK) but I think this problem may be nothing more than a very dead battery. Need to travel this week, so I'll give another crack at it this Wednesday / Thursday timeframe. Thanks for all the help.

Mark

 

When you have the battery tested, make certain it’s not just for voltage, it must be LOAD tested meaning current draw comparable to what’s required to start an engine, not just enough current to run the electrics. Need to make certain it’s at full spec, no bad cells, etc. Even new batteries can be duff, so age isn’t the only thing to go by.

 

As jahummer says, load test the battery.
When you say that your battery is a regular size battery, is it not the battery that is specified for the car (H8, size 93 if I remember correctly)? These are a very large size for a car battery with 800+ CCA. A regular battery from the family sedan won’t hack it.
And make sure a new battery if required is fully charged using a 10 amp or larger charger, not a trickle charger or maintainer. Off the shelf batteries at the store will not be fully charged.

 

You are correct that the 2nd battery that I tried was a lower amperage / normal sized car battery. It was just a test to see if the car would power up and turn it over. It did not turn the engine over. It’s almost hard to believe for a 4.2 L size V-8 engine that a normal car battery wouldn’t turn it over. This car control system must demand a lot of power. With 2 (175) amp fuses which I don’t know where their located yet I guess I should of expected it. I will load test the original battery. Local automotive stores have digital load meters where they actually program in the specific battery and load test it accordingly. What I don’t understand is why this car drains the battery so quickly just because you don’t lock the keys on the remote. I think this was the reason it died once before. I wish there was a way to eliminate this feature. At least I understand from this forum that for a longer period of time the electronics drains the battery after the engine is shut down if the keys are not locked. Perhaps my battery is part or the main source of my issue. Either way it’s unbelievable a battery that’s less than two years old would exhibit this problem. This is one massive battery. I need to come up with a slide tray designed removal system keep having this dang problem I know that.

 

Locking the doors will manually shut off Convenience Mode. If you park but don't lock the doors, Convenience Mode will automatically shut itself off after approximately 25 minutes - and that delay sucks power from the battery. Even when Convenience Mode is off, the clock and other modules will continue to draw power, albeit small.