Xj6 s.3 battery draining
 

Was having trouble starting. Thought maybe starter.

Battery died yesterday. Kindly old neighbor tried to jump start, to no avail.

Thankfully, he has charger. Hooked up for an hour, and then started right up.

He suggested electrical system draining.

So, for now, unhook battery when parked, then attach to drive. This works, but not a long term solution.

Suggestions?

Its also possible that your battery has reached its use by date, do you know how old it is? You can put a multimeter in series with the battery (car static and everything turned off) if you see more than a couple hundred milliamps then the battery drain story is worth pursuing(really a guess as I dont know what in your car, assuming a radio memory and clock would be all thats drawing)

Battery drain can come from a variety of sources. Look for obvious things first , make sure all you interior lights are actually turning off, check the boot light turns off when you operate its switch by hand.

If you do tinker electrically you can trace sources of drain by measuring at fuse points, this is made more interesting in our cars as fusing is somewhat distributed. There are numerous Youtube videos on this topic, some of the better explanations are on the ETCG or Briansmobile channels.

If you arent electrically inclined , I'd be straight off to the auto electrician.

Other more knowledgable people may be able to suggest common causes.

the battery could be dying, not holding a charge.

if the battery is good and fullly charged, then check each door warning light by pressing the door jamb switch on each door jamb.

there is a light at the rear part of each door, you can see it when you open the doors. Though they normally come on when the headlights switch is in any of its ON positions, sometimes they stick in the ON mode.

if none of that is causing the problem, look for any added switch that a previous owner might have installed.

Thx.
Sometimes the third brake light - a worthless invention - seems to be staying on, even when car is shut off.

Possible to disconnect?

Thx.

Yes, it can be disconnected....although I can't remember the most convenient place to do so. Perhaps right at the lamp itself.

What year is your car? Is this an add-on brake light or factory installed? Factory installations began in '86 as I recall...and the circuit is powered-up only with the key 'on'.

Cheers
DD

thx. It's an 86. Factory.

Third brake light:

I'm thinking you have some sort of back-feed situation going on. Mulling required; not sure where to begin....but faulty grounds can have extremely strange results.

Any sign of weird wiring hacks by previous owners or mechanics?

Someone mentioned the door lights staying on; worth checking. If that's happening AND your power antenna isn't working, check the power antenna fuse. If the fuse is blown a back-feed will occur and power-up the door lights. Jaguar was aware of this an issued a tech bulletin to address the issue by adding a diode into the circuit. I can't remember if this fix was incorporated into production or if it was always an after-the-fact thing.

Cheers
DD

was over thinking.

Battery was toast. Thx

to disconnect the third brake lamp:

press under the cover, there are two push-up Tabs, and carefully pull the cover off, same procedure to replace the GE #194 bulbs, i.e., remove the cover.

you will see on the right side of the lamp a grey connector with two thin wires.
carefully pry it off and that's it.

Ideas:


1. I like the idea of a top high mount third light. My 83 does not have one. But, I am not going to "monkey" with it's electrics.


If indeed, it is powered only with the ignition switch in "run" and it is on with the switch in "off", I see the switch itself as a cause. They wear out. Age and heavy key rings. They are not that robust. Been there done that.


2. Just remove the bulbs. leave the wires intact. less chance of odd results.


Caveat. I don't know if the lack of bulbs will trigger the bulb failure lamp on the fascia.


A review of the S57 schematic should tell if it is.


All folks with old cars should have battery chargers !!! I am no longer
a fan of jump boxes or cables. But, at times, it just has to be....


Carl

Nope!

The CHMSL (Center High Mounted Stop Light) is not wired through the BFM (Bulb Failure Module)

Cheers
DD

Carl, it is very easy to update your car to a Top Center Mount stop lamp:

there are only two wires, one is a Ground that can be connected anywhere to the body.

the other wire is 12v power. I connected mine to the tail lamp Stop light bulb wire, running the wire to the trunk through a hole that is already there with a rubber grommet.

No issues, zero, nada, works perfect. The Bulb Module continues as normal.

To stick the lamp to the glass, I used 3M double stick tape. Just get it centered and as close to the bottom as possible, but leaving space to get your hand under to remove the cover.

I would have preferred it at the top of the glass, BUT, it interferes with the rear view mirror view.

My 77 S2 XJ6C starts quick, but when parked has a 25ma draw on the battery. Would that be for the analog clock ?

Could be.

25ma draw is about right; shouldn't cause a problem

Cheers
DD

place a cel phone in video recording mode inside the boot / trunk, close the lid for a few moments and then open it.
Check the video to see if the trunk light went off.
Same with interior lights, but with all doors closed you can check if any interior light stays on.

Some years ago, I had a similar problem in my S3 Xj6.
It was leaking about 1 + amps and would flatten the battery in a day or so.
I found the leak by putting a multimeter between the battery and the main battery lead.
Turned out to be a "leaky" diode in the alternator. The alternator still seemed to work OK i.e., produced charge and no warning light.
A new diode plate fixed the problem.

Finding the short.
 

Used the VOM to determine the draw. 25. ma isn't much, but finding the leak, the short is harder. Usually start by pulling fuses to limit the search area. There is a reason battery disconnects are common on old cars.

Anyone is free to do as they please, of course, but tracking a 25ma draw is time that might be better spent elsewhere on an oldie Jag :)

That amount of draw does not represent a problem by industry standards.

From this website; there are others expressing the same.

https://continentalbattery.com/blog/...g%20its%20life.

“Typically, the normal amount of parasitic draw is between 50 and 85 milliamps in newer cars and less than 50 milliamps for older cars.

Cheers
DD

None of my older Jaguars (Mk1, Mk2 and S3 Xj6) are daily drivers. More likely once a month.

Even that miniscule 25 milliamps (Ma) that Doug mentioned amounts to a serious drain on a battery over a period of 30 days X 24 hours a day = 720 hours.
720 hours X .025 Ma =18amp hours which amounts to a fair loss in capacity. Take that up to double with 50 Ma and 36-amp hours and you are definitely getting close to a flat battery.

Consequently, I have fitted quick disconnect battery devices to these cars so there is no parasitic drain on the batteries.
With a regular top up with a battery charger I am getting a typically 5 year battery life and a good start every time

Apologies!
I should have mentioned in my previous post that the average car battery capacity is between 40 and 65 ampere hours.