Agree Bob...a circuit is using volts when she's turned off. What if it's the ignition switch or courtesy lighting module/relay?

 

I've got to come up with a way to be able to detect normal versus unusual load after the car is turned off.

Then once I see that it's happening I may be able to find the culprit.

The SOB is intermittent.

Any ideas on measuring current load so I can observe it once the car shuts down?

No lights are being left on that I can detect.

 

As it's probably a small current and as the car anyway takes up to about 40 mins to shut down, you may not be able to use a current clamp (I'm not sure how sensitive they are at small currents but not much good I think). They're not wonderfully cheap (or accurate) anyway. Have a look around, though, and see what you think. You'd clamp its sensor around a wire leaving the battery (or any other you suspect).

Otherwise, probably just a regular meter to measure the current. Snag is that it'll have to be in series to do that so you'll need to disconnect the battery and also have the meter on a sane range (start higher and work lower). I don't know what the current drain is after (say) 2 mins and with everything closed/off - less than 1A I guess, but it might not be.

The modules shut down progressively (well, are meant to). They send each other messages as they decide to do so, at least some of them do.

There's a TSB or part of JTIS that has a little detail but not much as I dimly recall. I think you're supposed to get say 50mA or less after about 40 mins.

You might as an alternative try touching relays after the 40 mins to see if any are still warm. If the problem's a module and a relay happens not to be involved, that'll be no help, however.

BTW, the glove box light is one of the things to suspect!

 

Dang jagv8! Good call...I mentioned a possibility with the courtesy light module/relay but didn't think of the glove box light switch. That little bugger gave me hell in a Stang. Bob, sneak into the glove box a few hours after shut down and see if the bulb is hot. Or just take it out and see what happens.

 

I am not sure that would help? The S Type has a power off cycle which should shut off everything in about 45 minutes. You can check this by leaving the trunk open and looking after an hour or so.

Now what might be going on is something keeps waking up the system which resets the 45 minute clock starting it over again. Of course the module could be bad too but it has not been reported so not common.
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The glove box light has been reported as the culprit on the UK forum. As has the REM (more often). I think a relay has been, too. (And of course damp / water in the trunk.)

This isn't a common problem. (Which doesn't help Bob.)

hmm, any dodgy wiring due to aftermarket stuff...... contact Jason........

 

I think it's haunted ...

 

So I had my car in for some front bumper repair and rocker panel painting on one side near the end of January.

As I dropped it off I noticed the old low battery bug-a-boo once again. It sounded a bit slow when I moved the car at the body shop and I thought uh oh.

So .. they informed me that they had to charge the battery and I explained the situation. A week later I picked up the car and all is fine except that the auto up/down windows have to be reset again and the transmission has been sent back to grammar school once again.


Move along for about another 3-4 weeks and I get in the car one morning and it's done it again.

So we're making progress as the intervals are getting shorter and something might actual fail so it can be identified. At typical Jaguar deaelrship hourly rates I' not about to take the car in and have them embark upon a long snipe hunt.

What I have noticed the two times I kept driving the car after an intial indication of a low battery, such as slower start, it does not seem to recover any battery charge as a result of driving it. I haven't tried a couple of hours because frankly I think I might get stranded.

I think this because after driving 15minutes to 1/2 hour it seems even worse at the next attempt to start the car. It beeps like hell and usually doesn't start in that case.

I'm beginning to suspect the charging system is either periodically not charging though I would think I would get a code for that or the alternator is actually draining the battery due to some internal failure and that failure seems to continue even after the car is barely started and run for 30 minutes.

But if I disconnect the battery, charge the battery and then resume operation everything is normal again for months or in the last case less than a month.

The next time I may just disconnect the battery and let it set for a couple of hours then reconnect it, get it started (if it will) and see if the battery begins to re-charge while driving.

I'm going to look at the systems voltage more closely during all of this as well.

Perhaps what ever is staying/sticking on continues to do so and cause the battery to not get re-charged when this is happening.

Having something like this in the car all the time might be helpful too.

Amazon.com: Vector VEC008 Digital LCD Voltmeter 12 V Battery Tester: Everything Else

Maybe this one would be a better choice

Amazon.com: BatteryMole Car Battery Warning System (12 Volt Automobile Battery Monitor with Battery Failure Prediction Logic). Made in USA: Electronics

I really like their "about us" web page

4peaks-tech.com

 

This has to be driving you about nuts. Being stranded is a concern for sure - do you carry a battery booster pack (aka jump starter pack) with you? Might be something to sock away in the trunk for now just in case.

I did see a Black and Decker battery charger that also had an "alternator check" function to it...not entirely sure how well it works but is intriguing.

Amazon.com: Black & Decker BCS25EB 25 Amp Simple Battery Charger with 75 Amp Engine Start: Automotive

 

Well it crapped again yesterday morning but it was a bit different this time.
I had a very early dental appointment which I never made.

I started the car and it sounded a bit slow in starting but not alarming. But my guard is up!

Then I dropped off my wife and went to get a full tank of gas so I stopped the car. That's about 15 minutes of driving.

When I restart the car it's slow and the "CATS System Failure" message comes on. So I cancel my appointment and go straight home. That's about a 4 minute drive. I leaving it running and slap a volt meter on it.

It reads 13.8 volts. Hmmm it's probably charging then.

So I turn it off and restart the car. it sounds fine and no issues. The faikure message is gone. This is definitely a weird voltage issue. I repeat this about 8 times. All is good. So I leave it alone for the rest of the day.

At 6:00pm I pick up my wife and it sounds slow again but no messages. I run the car for about 40 minutes as we're picking some stuff up and then park it for the evening.

This morning the battery reads 12.4-7? volts and the car starts great. Once running the voltage reads 14.2. That seems high to me?????

The other times I always charged the battery and re-connected it. This time I just observed.

It's such a new battery and when it started doing this it was less than a year old. Plus it happens so infrequently except of late that I still think it's not the battery.

 

Can you check each cell with a hygrometer? IMHO, the sp. gravity of each cell is a better way of checking battery functon.
Long time ago, I had a somewhat similar situation, the battery read 13 + volts which looked good, but I rechecked it with a hygrometer and two cells were weak. Replaced battery and all was well.

 

The alternator is told (by the PCM) what voltage to charge at. It uses a higher voltage at some times, mainly when car just started from cold, then switches to a lower one. All explained in JTIS. Your voltages measured when running fit that.

However, everything else sounds suspiciously like a failing battery. Or, I suppose, something we're not used to here. Beats me what but if certain the battery's OK then the long list of stuff any car can suffer (bad power/ground being biggies).

 

The good news is that it's getting more frequent so hopefully a hard failure is imminent and then I'll have a definitive answer.

In the meantime I think I'll get one of those portable power packs and carry it.
That way I won't get stranded or miss any more appointments.

 

Maybe it's something such as a cracked battery post. Usually connected but varying in how well.

 

I do still have the old battery which I use in my race trailer for operating the winch so I could swap it out and see it the problems disappear.

Or I could just blow another $100+ on a new battery and see.

 

Before you purchase another battery, make sure you do these simple things first:

1. Remove your battery terminal clamps, clean them, and burnish them.
2. Clean and burnish your battery posts.
3. Remove your battery ground screw, clean it, burnish it, and burnish the metal frame where the screw grounds into.
4. Re-attach your ground screw, ensuring it is tight.
5. Re-attach your battery terminal clamps, ensuring they are tight.
6. Check the water levels in all six battery cells. Fill as needed.


Perhaps these actions will resolve your problem. For maybe 15 minutes of work, it's worth trying if you haven't already....

 

All of that got done when the battery was changed over a year ago.
That battery was showing zero symptoms but it was I believe the original si I thought it prudent to make the swap in advance to avoid issues JUST LIKE THIS ... ARGH!.

Zero signs of any corrosion at that time.
It was a garaged and babied car wityh only 14K miles on it so that's waht I would have expected.

The battery terminals have been on and off quite a bit since then ...
Once again, I just don't see any of that.

I'll look at the water today though.

I've never heard of battery having an internal short that comes and goes, mostly goes?

Anyone else heard of this?

 

Next plan might be to check battery voltage each time before starting. Then try to start the car. See if any pattern occurs or anything is obviously suspect.

You may have a slight current draw, leading to a low voltage, but you won't know till you take some readings.

 

Well hopefully this is an announcement of the end to this saga.

Three weeks ago I went for a round trip drive that lasted about an hour so that included two start-ups. There was no indication of trouble and when I pulled into my driveway I was listening to something on the radio that I didn't want to miss. So I turned the engine off and then turned the key back on.

Well shortly after that I got so many strange failure lights that I decided to turn it off and then see if it would restart. Well it did start but sluggishly and I got the dreaded dead cats messages again. I'm so tired of all those dead cats ...

I went to the trunk, measured the charging voltage - normal then I measured the batteries voltage 11 - not so normal.

All of this happened within a couple of minutes.

My conclusion is that the damn battery has got some kind of an intermittent internal short. If the car had dragged the battery down that fast (a couple of minutes) I would think something electrical would have burnt up in the process?

So I threw out all those damn dead cats and put the old battery back in the car.

It's been running flawless now for about three weeks.

So yesterday I took the battery back to Pep Boys and and was greeted with a load of skepticism. Intermittent failures are tough problems. They insisted on a battery (moan) of tests which included a full charging of the battery. I insisted on a long lunch ...

My BBQ pulled pork sandwich, coleslaw and birch beer was tasty.

BUT NOT AS TASTY AS THE RESULTS OF THAT TEST!

WOO HOO it failed!

Jeez, I really hope this is finally the end of this crap. (I tried to find a dead cat ...)

BTW, during the last 3 weeks of using the original battery I think it actually drove better. Except for that occasional automatic window failure thingy ...

One mystery at a time!

 

Wow, I sure hope you've found the cause!