Hello guys;

This is scaring me now.

This started with a battery light ocassionally. Then car started dying at stop lights, battery fully drains quickly. Replaced ALL battery cables and alternator. Still the same problem.

My mechanic had the car running with the a/c on for about an hour and the car ran fine after installing the alternator

While at the shop i left the car on with the AC on and the lights on (BTW I always drive with the lights on) and the car died again.

So it's not the alternator or cables.

Something is suddenly draining the battery quickly-

Because I am always driving with the lights on I am thinking it's something with the light circuit

OR

Because the first time the car died was after a car wash I am also thinking water in the ECU

Please help !!

 

I should add battery does not die if left overnight. Only when car is running

 

WOW, now it is getting down to something running or trying to run while the car is on and it sucks the power down..

Let's start here first, since it is more associated with the A/C being on...Does the radiator cooling fans run at all while the A/C is on and the car standing still idling for a while, with everything up to temps and hot?...If no, this could be drawing the voltage down as they or the fan module maybe shorting out when they are called for to run.

 

They did test the fan module

They did extensively test the battery and new alternator and both where charging normally until everything the lights with the a/c on high where on and then the car died within a few minutes and could not be restarted. What can cause such a huge drain so quickly?

 

Mark,



sorry to hear about your drain issues with the X. .



Are you saying that a fully charged battery is drawing down to empty within a few minutes or is it taking an hour or so? I know on a lot of newer cars the ECU acts as a switch in a sense deciding when and how much the alternator will recharge the battery under different conditions. You can test the alternator on some of these systems while the car is running and it can appear that the alternator is not working correctly but in reality the ECU is not allowing the alternator to recharge as needed because it is controlling the regulator that is in the alternator. I suppose if you have enough draw on the system and the alternator is not allowed to recharge as needed you can pull down the juice in the battery pretty quickly.

Just some thoughts on what might be causing this so hopefully others on here will have seen this before on this car. I know I replaced a alternator years ago on a Honda because all hooked up on the car it was not showing to be charging but came to find out had a short in the wiring between the alternator and ECU which was causing the alternator not to charge while hooked up and car was running. I bring this up because it is possible that if the ECU got water damaged in a car wash this could be causing the issue as strange as it might seem. There should be a testing procedure through All Data to see if issue is related to ECU either internal or connections etc.

Getting more complicated to diagnose these type of issues on the newer cars as sometimes what appears to be going on is not always that simple.

Good Luck.

 

The only reason for a battery to drain quickly, I can think of, is to have a short circuit somewhere.

When the battery is dying, are the main cables (connected to the battery itself) hot?

 

This really sounds like a short circuit. But not a direct short to ground. A direct short to ground will arc like a welder. Your battery will get REAL hot and it could start to melt insulation around the battery cables.
This sounds like a short through a resistor of some sort. It will probably be something like a loose wire or something effected by the movement of the car.

You did say that with the car off the battery does not drain, so it is probably the car moving that is causing the short.

You need to do some troubleshooting. Start with a fully charged battery and turn everything off. Lights, radio, fans, everything you can.

Then look at your amp gauge if you have one. Note the reading.

Then turn things on one at a time while keeping an eye on the gauge. If you see a jump when you turn something on, you have isolated the circuit.

This is probably something loose or something draining slowly and it may not show up with the car on, but parked, so duplicate the test while the car is moving. (this is one of those times when a co-pilot comes in handy.)

I once saw something like this when a light bulb socket failed. The light bulb still worked, but the socket wiring was shorting.
I have also seen this with a short around a spark plug, and even a fan motor that sucked up a small rock that chafed a wire in the winding.

These can be a real bear to pin down. So knowing which circuit the short is in is vital.

Good luck and keep us posted.

 

THANKS much for the replies.

The car died while sitting at the shop on, in PARK with the A/C and the lights on. Probably not motion related.

Retracing my steps I can only think that the first time my car died was right after the wash, that is why I was thinking ECU, but I have zero codes.....you would think that a water damaged ECU would be throwing all sorts if codes .

The reason the headlights also came to mind is because I always have them on as because I replaced both headlamps recently the passangers side headlamp connnnector disintegrated in my hands sort of, so maybe there is a short there.

 

Mark,

I would say to start with the basics and work from there. You would think that if the connector on the back side of the headlamp had gone bad you would see a blown fuse when lights were turned on or at some point in driving the car.
If I remember correctly, you had said that when the car died and left you stranded that the battery cable got very hot. Did the new battery cable get hot this time when it died at mechanic shop? Do you know if the battery is getting recharged from the alternator with a/c and or with headlamps on? Easy enough to start with a fully charged battery and then see if and when battery is not getting recharged. This will help to narrow down the possibilities as to what is going on. I would not assume that the ECU would throw codes if water damaged but my approach would be to get the facts from testing to see exactly what is or is not happening when car is running. Once you know the exact readings you can back test to figure out what the source of the problem is.

Good luck

 

Do you have a multimeter? Set it to read in Volts of DC Current (VDC).

Step one is to check the voltage at the battery terminals themselves. (Not the battery cable clamps.) This should be between 13.3 and 14.7 volts.

You say you have a new alternator but do you know it is putting out? Put a multimeter on the terminals and check.
First check the Alternator coils. You should see two small and two large connectors.
Put the multimeter on the two large connectors. The output of your alternator should be slightly (.2-.4vdc) higher than the reading directly across your battery terminals.
Next check the field coils. These are the two small connectors.
When the alternator is under load this should be about 5vdc with no accessories or lights on and approx. 10vdc with the accessories on.
If this all checks out your charging system should be working.

Next follow the wires from the Alternator all the way back to the battery. You will find some other items in line before you get to the battery so check output on both sides of all these items.

If you get to the battery and are still showing 13-13.5 volts your charging system is working.

I suspect you may find a voltage drop in one of the components between the output of the Alternator and the Battery.

Make sure you look for fusible links. These look like lumps in the wires.

 

Thanks for all the replies again !

Problem may or may not be the ECU

The headlamp wiring theory did not pan out. Mechanic has been looking for a short circuit all morning and can not find one. It's unlikely the problem is the new alternator because it was doing the same thing with the old one. He has traced wiring from the ECU and can not any type of short.

He thinks the battery may be defective and is going to try a new one. After that he will start looking at the ECU itself, although he has not seen any damaged ones in other X's.

Fortunately it looks like the X TYPE ECU''s cost too much, a new battery will probably cost more.

 

New battery does same thing. alternator and battery ruled out. Doing pin-out test of ECU next . At some point water was leaking inside the passanger side because of a ill possitioned windshield cover. Has anyone had water ingress in their ECU's??

 

Just in case it's my ECU, will any 3.0 ECU work? How do I know which one is compatible with my car?? has anyone had ECU problems ?

 

Mark, if it ends up needing a ECU I would check with both a Jaguar parts dept and a wrecking yard that specializes in Jags to see for sure what years etc. are compatible or interchangeable with yours. I would assume that you have a federal emission equipped car so I would think you would want to stay away from a California spec. ECU if you find a used one.

I would think a used one will be considerably less than one through Jag but there may be re-manufactured ones that will be fairly close to the cost of a used one but will have a warranty with it.

 

Spike, I would start off by connecting a multimeter across the battery and starting up the car with nothing on. You should see the multimeter sitting at 13.7 VDC and be pretty steady. I would then turn on just the headlights (turn off as much other stuff as you can). Does the lights cause the voltage to drop at all? If not, then the problem is not directly related to the headlights. Next, turn off the headlights and turn on only the A/C on MAX (fastest fan, as cold as you can make it). Does the voltage drop now? If no, then the problem is not directly related to A/C system. If the voltage does fluctuate, then back off the temp and fan speed to put the A/C system in a condition that it will only run the fans periodically. Does the voltage remain low or did it come back up when the fans are off? If low, then your problem lies with the A/C circuit. If it cycles on and off, then you are looking at problem with the A/C system. That will hopefully narrow things down.

From what I can tell, you are looking at a draw of like 200 amps or so to be killing a car and killing the battery as fast as you are saying. Any sort of wire on the car is going to get really hot under that sort of condition. I would say to get your hands on an IR camera and see what is hotter than the surrounding area and what shouldn't be as hot as it is. As you can imagine, there is not many circuits in the car that can even remotely handle the power you are talking about. I would take a good look at the power wires running to the fuse boxes to make sure that they are not making intermittent connection and resulting in the drain you are seeing. That would be the most likely wiring that you haven't checked that would result in what you are seeing.

I will attempt to assist however I can.

 

Thermo -

Could it be possible that the starter is not disengaging? That the relay is just chucking the starter gear out there and powering the starter constantly?

Isn't Spikepaga the fellow here who has had all the "runnability" problems, too? (too tired to look). Could a stuck-in-start starter cause both problems?

 

Bruce, if the starter was stuck engaged, first off, think about this, if the starter spins at say 3,000 RPM to make the motor spin at 300 RPM, how fast would it be spinning if the engine was brought up to say even 3,000 RPM? I would say that is faster than the starter could remain together in 1 piece. Not to mention, since the motor would be driving the starter (assuming that it can handle that kind of RPM), it would actually turn the starter into a second alternator. Since it is unregulated, it would be pushing the system voltage sky high, frying everything. So, overall, I don't think it is the starter remaining engaged. If the gearing let loose of the flywheel, but the motor portion was still spinning (due to power being applied), the current draw is very little (under 20 amps or so) since there is no load on the starter. A simple check would be to start the car, put it into the condition that the fault occurs and then feel the starter to see if you can feel it spinning (may need to feel for a vibration difference between the passenger side of the motor and the starter).

 

No it's not the starter for sure. That was tested.
With full load on the alternator charges exactly like its supposed to in gradual steps and then it abruptly falls flat and stops charging. It's got to be a ECU or a ECU to alternator issue.

Anyone can tell me about ECU compatibility??

Thanks so much

 

Sounding more like the ECU all the time..I admire your sticktoitness...

I think the ECU has a thumbprint so to speak of the car so it can only work with this car with this VIN..but the new one will have to be programmed to meet or match your car's personal profile before you can start it..it has something to do with the security system too...Call a Dealer and ask the service people..they'll surely be able to tell you, or maybe a JAGTECH here will be able to help..

 

Just to add another four pennyworth! Spike, I note that earlier you said your mechanic had traced the cabling from the ECU to the alternator and found no evidence of a short, but did he check for open circuit? If there's a short on the alternator signal wire the charge goes to max, but if there's a break in it it goes to no charge. There may be a suspect connection or intermittent break in that line?