Hi guys. I'm hoping you can help me. My dad is a retired mechanic who lives 4 hours away. I have the benefit of things he taught me all my life, but he's not familiar enough with Jags to help me over the phone.

My gorgeous boy is having problems. He has a battery drain and I got around that for a while by disconnecting the battery when I parked him for the night. That became a problem as soon as I discovered that disconnecting the battery wipes the BPU and then there's no way to pass emissions.

I read up on checking fuses and even purchased a multimeter. The process seems so overwhelming that I haven't jumped in to that yet.
I replaced the BPU because that seemed like a good place to start based on what I've read in these forums. When there are battery drain issues, the BPU is a likely culprit. This did not solve the battery drain.

The ignition switch has gone bad twice. I start the car by turning the key and then sticking a jump wire in the proper holes in the correct big black plug thing near the front bumper. I forget what it's called.

I am at my wits end. I am considering replacing the ignition switch again and selling my beloved boy to someone with more patience and money. Any advice? I'd love to keep my car. He's gorgeous and really REALLY loves to get on the highway.

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1996 XJ6 VdP (added by GGG)

 

I've seen the amp for the stereo be a common problem for battery drain as well. Does yours have the amp for the stereo?


Otherwise, you will to do a draw test. I'd get a jumper wire with some alligator clips on the end, and you'll need to get your multimeter. Open all the doors and manually latch all the door latches while the doors are still open so you can have access to all the fuse boxes. You will need to do the same with the hood, manually latch the latches leaving the hood open. Then disconnect the positive side of the cable, install your jumper wire between the cable and the terminal on the battery, leaving cable disconnected. Make sure you do this before connecting your meter. Make sure your meter is set to amps, with the leads plugged in the correct terminals. Place your multimeter inline between the positive cable and positive battery terminal. After 30-40 minutes, the vehicle should fall asleep, and should be reading .040a or below. Anything above will indicate a draw. If you do get a reading above .040a ( 40 miliamps ), you can start pulling fuses one by one to see if the reading drops, it should drop straight to .040a or below. Which ever one drops, see what that fuse operates, then you'll need to go forward from there disconnecting any modules one by one with the fuse back in to see if goes to sleep.


If you need anymore details, let me know.

 

<deleted - no longer relevant>

 

I've moved your question from X350 to X300 forum and added vehicle cdetails to your forum Signature as I requested you do in my reply to your Intro.

This is the place to post technical questions about your model.

Graham

 

Karen,

First things first, I'd recommend you pick up a battery float charger - BatteryMinder, Battery Tender or CTEK all come to mind, but anyway, a method to maintain your battery charge overnight without resetting your emissions monitors, so you will be allowed to remit the required tax to the fine state of GA and be on about your business.

That's just a bandaid - you have a lot of work cut out for you to sort the problem. Although in the S-Type section, I think you could use this excellent guide, modified for X300 to methodically track down your problem - https://www.jaguarforums.com/forum/s...-drain-123535/
You'll need a DC Voltmeter.

Maybe take another stab at explaining how you start the car? That is most assuredly not normal and needs be sorted as well. Maybe pictures of the component you are inserting a jumper wire into? BTW, the service manual and wiring guide are available for free download in the stickies.

 

Yes on the trickle charger to keep you from disconnecting the battery . I would recommend the mastery / big picture approach to honing in to the issue resolution . And I have some shortcuts for you with this approach . Alot of the Jaguars wiring goes though the 5 fuse boxes by way of the boxes terminal post . If you remove the posts ( 15 mm deep socket or open end wrench ) one at a time and test the amperage draw you look at a 20 fuses at once . Once you determine which block is staying awake and draining the battery you can remove one row of fuses to get down to 10 fuses to focus on . You can test the amperage draw in a way without a current sensing multimeter by measuring the voltage drop ( as the battery can still be hooked up but no charger ) for a " same " specific time say 1 or 2 hours for each fuse block . Will need to recharge the battery for each test for the voltage / charge curve is not linear or straight . Based on percentages I would start with the 2 heelboard fuse boxes behind the panels below the rear passenger seat pan near the carpet and then in the trunk the one aft of the battery . You may or may not have a fuse map so see the document below page 21 keeping in mine the # 1 fuse is the one next to the terminal post . Any questions just ask and someone will assist you .

 

Forgot to mention the fuse boxes post are hot at all times so disconnect the battery or be aware of it as you tinker with the post . If you have any questions you can private mail me , see wiring schematic below page 31

http://www.mediafire.com/file/fiqsbb...e+-+JTP508.pdf

 

I would be inclined to bottom out your ignition switch problem as a first step.
At the risk of tempting fate, my car can sit locked for extended periods of time, and start on the first turn of the key.
However I have inadvertently left the key in the ignition, in the fully "off" position a couple of times when I have had the car in the garage working on it, and the battery doesnt last 24 hours. Something must be drawing current from the moment the key is inserted.
On more modern cars inserting the key starts a powering up sequence for things like satnav, climate control etc, even before the key is turned. I am told a modern Range Rover will draw more than 10 amps from the moment the doors are unlocked.
Whilst the X300 isnt burdened with as much technology, something definitely starts to draw current when the key is inserted. If you ignition switch thinks the key is in, that could explain your problem? Might be worth a look, and unlikely to be a waste of time, as the car is effectively undriveable if it wont start from the key.

 

Be aware that the BCM (Body control module) alone consumes extra power & continues while ever it is activated. For instance if you leave the boot open for a length of time. When initially opened the lights are drawing power & the BCM but when lights go off after a time interval the BCM still remains active ( using power) while ever the boot is open. This same procedure applies to doors open etc, I measured a draw of 40ma with boot closed (normal drain) however with boot left open 240ma was being drawn, biggest part of this being the BCM.
The previous article mentioned is a good guide to the problem & is basically based on the official Jaguar/Landrover "Battery care Manual" that I have attached.

John Herbert