My 2004 X-type, 3.0L, AWD has one perplexing problem and I believe I've read all previous threads regarding this issue.

Randomly the battery light comes on! Once it's on it doesn't shut off until the vehicle is shut off.

What I've done:

I've checked all positive and negative contacts and they're all clean and attached properly.

I've checked and there are no burned out fuses.

Using the diagnostics activated in the turn signal stem I've monitored the alternator's output voltage. Output ranges from high 12 volts to high 14 (which I think is proper) and I've not seen any correlation to alt output and the gremlin battery light!

I recently had the battery replaced and thought that had solved the problem. The light didn't appear for almost two weeks, but... it's back!

In prior threads it's been suggested that the resistance of the positive / negative wires increases as the operating temperature rises. I haven't witnessed any correlation to temperature (ambient, or operational) and the appearance of the battery light. There have been times when the vehicle has been non-operational for 12 hours, or longer and the light would come on within seconds of starting with ambient temperatures under 70.

But in case the wire gauge isn't adequate, or wire degradation over time is having an effect, I have some 0 gauge high quality copper wire and as soon as I find a local Jaguar mechanic I'll replace all of the pos/neg wires.

So I can't say I see any pattern at all for when the gremlin decides to show up!

Has anyone with a similar problem found a solution?

Your experience and input is greatly appreciated!

-M

 

Cables ends always seem to LOOK okay...it's the cables themselves...REPLACE THEM ALL!

 

Did you have this problem and was that the solution?

 

Yes...Your symtoms mimic exactly what I was experiencing..I did a wholesale change out and cleaned the ground end bond to the body of the NEG cable and even ran the short POS to the fuse box too..essentially ALL the heavy battery cables...I was able to resource all of them from different places on the internet, but it's doable yet I would think..I went with OE only so everything fit correctly...I suppose a person could build up their own set from the local auto parts stuff, but I didn't want to change the original looks too.

I understand before somebody pipes in, that the problem maybe with just one of the cables, but I was not going to trial and error this.

 

Yeah usually you can see the sealant melting away from the cable ends at the terminals. When you experience the issue you can most of the time feel how hot the positive terminal is on the battery(suggest a thermometer though rather than touching. Very hot) fairly common

 

That's my next step!

Did anyone ever use cables other than OE?

 

You say you had to source from multiple places? How many cables in total did you need to change out?

-M

 

For what it is worth, you DO have a voltage drop. High should be about 15V, not 14. (yes, our cars are BRUTAL on batteries)

 

There is one long one from the POS post to the starter, then it goes to the alternator...Another red POS cable went to the bottom of the fuse box (those are separate CABLES, but are connected together at the POS battery POST....The two in the NEG set I believe are bonded together at he NEG post end...One goes to the inner front right just behind the driver's side head light assy (this one you should really clean the cable to body connection..The other NEG cable goes down under the BATTERY BOX and is bolted to the top of the transmission.




Oh and yes, you HAVE TO REMOVE the battery and the box to accomplish all this this.


I believe IIRC, that there is enough slack in the wiring to the fuse box, that you just are able to turn it over a little to get to the POS connection there.


Hope this helps.

 

What I observed were high 14's, almost 15. I thought that was the regulator ensuring it didn't overload.

 

Do you know of a source where I can get the cable specifications (length, gauge)? I can't seem to locate the info.

The cables currently in the vehicle look very tight, wondering if I build my own if I can increase their gauge.

 

Somebody around maybe able to help you..with all the JAGTECHS and all...you can see them in the JTIS manual..perhaps you can get one from someone here...I don't think dimensions (gauge, length) are mentioned per se, but you can see their shape and configuration I believe.

 

Hi folks. Here is the issue with my charging light. The light comes on at random times of the cars running so this morning I did a voltage check and watched it and here were the results. Initial results were as follows.

Initial start up an running voltage was between 15 - 16 volts and a strange noise from alternator.
after warming her up the voltage dropped to 13.9 both with everything switched off or with every electrical item on the voltage stayed at 13.9 but the charge light is on so I turned car off stared her up again and this time voltage went to 14.4 and stayed there both with nothing on or everything on and no light on but every so often the engine revs would drop and voltage would drop to 13.4 but within a few seconds it would settle at 14.4 and stay there. If voltage is around 14.4 then the light stays out. I am thinking the alternator is on its lasts legs. I have added in an extra earth lead as it looked badly corroded at its anchor point and would not come out plus I checked for a voltage drop between alternator and battery and it was 0.02 of a volt so think that lead is sound. Any idea's

 

An update. I had car in my garage and went into the test menu on dash board to watch the voltages from inside the car. When I started it the voltage was 14.4 but soon shot up to 16 before settling at 13.8 which brought the charge light on. The interior lights and headlights are going bright and dull which coincides with the alternator charging rates fluctuating but it soon eventually settles to one voltage. The car revs also change as the charge rate changes which shows that the load is increasing and decreasing on the engine.Is there anything other than a faulty alternator that can cause this unstable charge rates. I hope that it does not spike anything with the high 16 volt charge it is giving out at times although the peak 16 volt is only for a fraction of a second before it settles but the ironic thing is that it is never dropping low enough to allow the battery to drain as the lowest it has shown is 13.8 volts with everything including rear demister on.

 

Had this. Replaced the battery. Took care of it.

 

Thanks. I removed the smart charge plug as I read on the auto files that it would revert back to normal charging if unplugged but mine does not charge at all if I remove the smart charge plug. I am no sure what it is as the lights go brighter and duller when it starts its dancing in tune to the revs going up and down but when it settles after a few mins it charges at 14.4 and no warning light. Might let it develop

 

I could be wrong, but I thought the voltage regulator inside the alternator was supposed to keep it's output within a range of 13-15 volts. Random 16v spikes sounds like the regulator may be on it's last leg.

The regulator should also aid the alternator when accessories are turned on by adjusting for higher outputs. There should never be any dimming of lights if everything is working properly.

Does anyone know if the battery monitor in diagnostics is measuring the alt output, or the battery output?

 

All I remember from my times under the hood chasing the fore mentioned cable problem..Is that when the car first starts there was a higher charge voltage for a few minutes, then it would drop to about 13.6v at idle and remain there until the next start cycle....It was describe in a technical manual on this as a means to re-charge the battery quicker after start-up to replenish the battery drain that took place during starting.

 

Thanks for replies guys.
From what I can remember from my time at tech when a battery is charging if it is low then the alternator puts in high amps but low volts until the battery is fully restored. As the battery starts to charge then the amps reduce and gradually the volts come back up to a steady charge of around 14v give or take a . here and there. My issue is that when it starts it's problem the charge is not constant. The volts increase and decrease and the engine RPM changes as the volt output changes. The spiking at 16v has only happened once under test. The alternator never fails to charge the battery but due to the uneven charge rate it occasionally brings on the charge light. When the volts settles at around 14v the charge light never comes on. Obviously when the voltage is fluctuating up and down then the lights will do the same as the voltage changes. I don't know if a failing battery will cause this uneven charge rate or if it is a sign that the alternator is starting to fail. I must stress this is only on occasions and is not consistent. Thanks

 

Not quite correct...The alternator is a regulated VOLTAGE source to the battery. Current (AMPS) is what the battery is drawing from the Aternator...By controlling VOLTAGE, it allows more or less current to be drawn by the battery..

For example; If you maintain 12 volts from the alternator to the 12 volt battery (equal, no difference in potential) "0" current will flow or be drawn..If you Increase the VOLTAGE to the battery to make a greater difference, i.e., 14 volts from the alternator to the 12 volt battery, then MORE current (higher AMPS) will flow..Which is what the aternator does right after a major drain on the battery, which by the way is rated in Amp Hours..or How long it can produce a certain amount of AMPS over a period of time. Once those AMPS are sucked out of the battery per se, also reducing the battery's output voltage, then the alternator replenishes them by re-charging at a higher potential voltage than the battery's potential, in turn, higher AMPS will flow back into the battery, bringing the battery voltage up to the same amount as the alternator is putting out and that's when you see the AMP draw fall off to nothing or very low at full charge.

Sorry for the lesson..I'm a retired Electrical Engineering instructor, so it's in my blood.