Two weeks ago my 2002 XK8 had no electrical power, not even a faint light or any sign of the faintest electrical current. I used a trickle charger overnight and the battery could not hold a charge.
I checked the battery and it was well over 4 years old so I bought a new one and the car started immediately and it has been running fine for the last two weeks.
Today I have the same issue. A completely flat battery. I have it on the trickle charger so I will check it in a few hours but has anyone had a similar experience?
There were no warning lights, no battery discharging indications, no sign the alternator was not working.
Could there be some intermittent short circuit in some system on the car that would drain the battery in about 36 hours?
All suggestions gratefully received.

 

Rob, you need to be checking for a parasitic drain on the battery.

If you have a clip on ammeter, clip it around the positive lead of the battery just after you remove the key from the ignition. On a healthy system you should be looking at 30mA.

Usual places to check are, the little flap in the ignition barrel is closing. All courtesy lights go off after 2mins. Security system locks correctly on the remote and courtesy lights go out straight away.

If you have your light stalk switch to auto and also your steering column, then switch them off.

Check this first and post back.

 

Any chance you left your key in the ignition?....This will not allow the electrical system to 'sleep' even in the off position.

 

JIM, I think you might be onto something regarding the parasitic power drain. I have noticed the steeering wheel does not adjust position on switching off on some occasions. I have switched the lights to manual and turned off the auto adjust for the steering wheel. I will now wait until the battery is re-charged and see what happens.
I did not leave the keys in the ignition overnight so we can rule that issue out.
Do you think I should disconnect the battery while it is recharging and touch the negative cable to the positive to reset whatever is going on?
Robert.

 

If you remove the battery for charging there is no need to touch the cables together, the time it takes to charge the battery will also facilitate the discharging of the capacitors in the system and therefore resetting it.

Good luck on your quest and keep us updated.

 

Not quite. There is a little flap in the key barrel. If it sticks in the open position, the car does not go to sleep. So you can have your key out, but it behaves as if the key is still in.

 

Jim,
Your suggestion worked like a charm, I disconnected the battery, turned off the automatic light switch and put the steering column adjust switch in the off position. I reconnected the recharged battery this morning and the car started up, no problems. I think I will always lock the car even when parked at my garage at home to make sure all the systems are off.
Thank you for your help with this little problem, I can now resume my drives to the beach with the top down in sunny San Diego!
Best,
Robert

 

My battery was drained again overnight! Barely 13 hours later the car was as dead as a dodo. I put the battery on a trickle charge and it started fine after about 6 hours of charging . This phantom power drain is clearly not giving up the ghost so easily. Headlights off courtesy lights off,glove box light off, trunk lights go off when closed. Steering column adjustment control off. What should I look at next?
About three weeks ago I had the seats out because I have a bad seat module which I changed over with the passenger module . Could the bad module be draining power? My next task will be to disconnect the power seat controls on the passenger side and see what that does to the battery. Does anyone have any other ideas?

 

Sounds like you have hit all the usual suspects. Probably time to read the current drain at the battery and start pulling fuses. After a couple minutes you shouldn't have more than the above mentioned 30 ma drain.

I don't remember hearing of a seat control module causing this sort of issue but the seat wiring is subject to rubbing with seat movement and blowing fuses.

 

The seat module certainly has the potential to prevent the CANbus from going into sleep mode and drawing down the battery (this is actually a frequent problem on certain Mercedes), but as you say, it is not a frequent problem on this model. Disconnecting is simple and definitely worth a try.

 

Just an idle thought unaffected by any real knowledge but seems I remember that the driver seat communicates on the CANbus because of the memory function but the passenger seat does not. The car comes with the same module in both positions but could the passenger module have been changed and/or worked in that position but is causing communications problems in the driver side?

Hope this is not an unproductive detour but inquiring minds want to know.

 

I had a problem with one of the seat modules a few weeks ago, I removed it and tried the repair to the PCB mentioned elsewhere but to no avail. In fact the seat back raised to the maximum extent and would not move. While I was working on it I noticed the motor that operates the tilt mechanism was very hot. I assumed it was because I was operating the tilt switch so I ignored it. I put the bad module in the passenger seat, the seat tilted forward and stayed there.
When I had my issues with a flat battery I recalled that the motor had been hot so I disconnected the tilt motor and I think the problem has been temporarily solved. The tilt mechanism must have been drawing prodigious amounts fo power and drained the battery in 36 hours or less.
That is my theory and it appears to be valid. No issues with flat batteries, all I need now is to find a new reasonably priced seat module. Are there any Ford modules that can be substituted for the Jaguar (Ford made) module at a more reasonable cost?

 

Both the Jaguar and Ford have seat control modules that look the same and both indicate 'made in Spain' but my efforts to determine compatibility stopped short of actually swapping.

The Ford units are readily available at wreaking yards and my Jaguar needs one. Anyone out there have any knowledge on the subject?

 

Even if they do use the same module, I think it is highly unlikely they have identical software loads.

 

Only a newbie here but this may help. There was a factory recall on my 2001 XKR because of flat battery/battery drain. Apparently, even with the wiper switch off there was an open circuit - the mod was to fit another ground wire. Maybe this helps maybe not but worth asking if the mod has been fitted. After my car was modded I have never had a problem with flat battery.

Steve

 

was this problem ever fixed? cause? I have it now!!

 

After the wiper switch recall fix I have never had any further problems with flat battery.
Steve

 

Hi Guys


I had same problem with my 2001 XK8. Battery kept draining over night, even when new battery fitted. Parasitic power drains are a pain to find. Usual suspects are alarm modules in door or boot light remaining on.


On my car, a auto-electrician used a code reader and found old fault codes in the system, which were cleared and the car then started first time. I've also had a battery isolator switch fitted in case the problem ever crops up again.

 

That switch must be a PIA. There are so many steps each time you cut the electrical.

 

I have disconnected my battery many times. What steps are you taking that I am not?