Hi everyone,

I have a 1991 XJ6 which has had a battery drain problem since I've had it (several years). The previous owner had mechanics and a Jag dealer investigate and they replaced the battery, but never solved the problem. Here's what I've figured out so far.

-I hooked up an ammeter between the negative terminal of the battery and ground. With the car off the current drain is around 200 mA, even after waiting an hour. It should be 30 mA.

-I started pulling fuses and found that removing C2 on the right side reduced the drain to the target 30 mA. This fuse controls the interior lights.

-I replaced the fuse. Verified that all lights work and all door switches work. When I leave the fuse out the battery doesn't drain over several days as it does with the fuse in.

Here's where it gets funny:
-When I open either front door the current increases to 300 mA, as would be expected.

-When I open either back door the current decreases to 30 mA.

So what's going on here? Opening the back doors do turn the lights on when the battery is hooked up, the same as the front doors. I'd really like to get this problem figured out. The car is beautiful and has only 60k miles. Everything works perfectly, except the battery drains after a week and needs to be jumped to start. Any insight is greatly appreciated!!!

 

OK, you are NEW, so welcome.

Your 1991 XJ6 is known in Jaguar world as an XJ40, confused?, worry not, you will get used to it.

I suggest you repost this in the XJ40 section, where you will get a flood of replies. The cars here are waaay different in many areas, and especially in the door innards.

If a Moderator picks up on this he may move it for you, but that could take a little while.

 

I should remain quiet, as I do not have any idea of the circuit logic in that car.
Or, this bit of logic if it could even be considered that. enough of a disclaimer?

The door switches are probably of the plunge type. Depressed, circuit open. Extended, closes the ground leg to the lamps.

So, an electrical "leak" aka low grade short in the switch or ground wire just might be your issue.

I messed with the switches in the door posts on the driver and passenger doors. RHD car and S3! I found the open in the driver post was well worn and erratic. Switching with the rear door changed nothing, but make the rear door no longer work!! I tried opening the switch to clean and repair. No go, too much lateral slop. I can activate the interior lamps with that switch by touching it and causing the post to move sideways. !!

Caveat again.

From time to time I use an alternate road to go on my errands. For years, I've seen a partly tarped XJ 40 in a driveway. Do I dare inquire?

Carl

 

The door switches aren't the plunger type in this case. They must be a part of the door mechanism, but I'm not really sure. You made a point I hadn't considered though. It's possible that the door switches do work (the lights go on when the doors open) but at the same time are leaking current when the doors are closed. Although, it seems odd that both doors leak the exact same current...

 

Welcome,

I looked over the wiring diagram and with the slight knowledge I have, concluded you may be best with a process of elimination.

Since all of the wiring for the interior lighting is triggered either by the console switches or the door latches (yes, there is circuit that runs to the latch mechanism) and all run to the CPU, you should disconnect one door at a time and re-meter the drain. I know its a pain, but I would disconnect one or the other rear door latches (circuit connection only). If that doesn't identify the source, then that would leave one of your console switches suspect.

Perhaps before you do the doors, you might place your meter in line, sit in the car and wait for the five minutes for the car to settle and gently touch the console switches just to see if one of them causes a change in the reading.

Good luck, be sure to report back so we know.

 

I measured the drain while wiggling the console switches gently and with each door open. Just wiggling the switches without activating them doesn't affect the current drain, so the switches probably aren't bad.

Here's something odd though. When the door are closed the interior light switch has no effect on current draw. When any door is open, the interior light switch increases the current being used. Remember that when either back door is open I get the lowest current reading. So turning on the interior lights with the back door open changes the reading from 30 mA to 200 mA, as does CLOSING the back doors... Keep in mind that all the lights, doors and switches function properly when the battery is plugged in. I was surprised that the switch didn't increase the current draw in all the conditions that would turn the interior lights on had the batter been plugged in. I'm not sure what to make of all this. Any ideas?

I'm worried that I'm not getting valid current readings with my mulimeter-in-line-with-battery method, because the interior lights don't work when I have the muiltimeter setup... Can anyone who has measured battery current lost comment on whether the electrical functions of the car worked during the testing?

 

This won't fix your problem, but it will be better than charging your battery every 3-4 days. I have been working on a 92 that has the same issue. I set my meter up the same way you did, I only have a 0.03 draw, but this battery is dead after a week. The battery is new as well. I have been chasing this draw for months. I finally put a cut off latch on the negative terminal, no more 13mm wrenchs. Latch up no power, latch down power. I still have to open the hood to do this, but it also gives me the chance to check out other things while I'm there. Eventually I will feed the direct source of this draw, but this is what I did for now. I did it on Friday.

 

Your draw is only 0.03A and the battery still goes flat? That's disappointing. I was working under the assumption that when I get the draw to that level it will solve my problem.

I do have a battery disconnect on the negative terminal, so I can keep the battery from draining that way. Now that I know which fused circuit is the problem I find it easier to remove that fuse than opening the hood and disconnecting the battery.

 

im having this same problem and i bought new car battery just to make sure if i give it jump the very next day it wont start and my button to lock the doors inside when i push it my passenger window goes down so im lost!!

 

Did we ever get a resolution on this one? Might be good to me because the battery drains over two weeks...

 

This might not be of any use Mick but in my driver's handbook, Jaguar recommends disconnecting the battery if the car is left to sit for 2 weeks or more.

Is yours draining when you leave it sitting or are you using it regularly and it still drains?

Larry

 

We had a peculiar instance in Champ once when we arrived home in the dark,shut the car down,and I noticed a faint glow from the courtesy light in the rear headrest.

Wha THA FA?
open hood ,undo battery,go to bed.
Next morn,hook up battery,performs normally,tried to duplicate and could not

I realized that the night previous I had moved the seat back extra far(good dinner)
When the seat is set up normally,no issue.
I cannot seem to replicate the problem,but I realize that wires do funny things with age!

I think that since the power seats are "hot" all the time I may have a slight short to ground thru the bulb,and back to the BPM.

I will find the cause one of these days......hasn't done it since.

Hope this helps,Cheers,Jim

 

Lawrence my car is a work in progress at the moment bit to do for roadworthy front is is in bits on the driveway but it does drain in two weeks if left without firing her up...and flattens battery totally dead so something is drawing power...from what I know which admittedly isnt much

 

Ok, gotcha!

Haven't had this issue (yet) but from what I've read it's time to start pulling fuses to see where the current drain is ...and good luck putting the front end back together, had the back end off mine a few months ago!!

Larry