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I'm just tossing this out to see if anyone happens to come up with something I have yet to think of....
Since the weather's gotten extremely hot on the East Coast, I've been having a completely random light-up of my battery warning lamp on the dash. It could be just a coincidence that the problem started when the weather changed??
It doesn't seem to be related to anything in particular and there's no pattern. It can go days without lighting and then come on for no apparent reason while motoring along. The car (2004 Jaguar X-type 3.0 AWD Automatic) lacks an amp gauge so all there is is the battery light to go on.
Turning off the ignition and restarting the car clears it and it might not come on again for another day or so. When the light is on, everything electric still functions normally. I've had the battery checked-out and a load test done on the alternator....everything checks out OK. I have yet to be able to check those though when the light is illuminated because it's so random.
I've checked the battery terminals, loosened, twisted, and then re-tightened them to be sure there's a good contact. No corrosion is present there either.
I've searched Jaguar forums and it seems to be fairly common. One guy drove with his battery light on for 90 days now. Others have been to the dealership, gotten new batteries, gotten new alternators, and even the dealerships don't seem able to correct it. It doesn't store a code either.
I know the jokes about Lucas Electrics and British cars, but this Jag has all Bosch or Ford components.
Thanks for the info. Mine has the same problem. I did put a new battery in it, but still randomly comes on. had check out and everything checks great. Probably something strange in the computer senors.
Is it that the voltage dips below a certain amount? If yes, then WHERE the voltage is being measured could be a clue to this problem.
You can get a low voltage situation with a low battery, alternator not working (I read you checked those), and with a poor electrical connection or too small of a wire being used from one point to another*.
*There is a thing called "voltage drop". You can have say a 10 foot long length of wire with a large electrical load on it. At the battery end the voltage can be 14 volts, but at the other end the voltage can be 9 volts! (Due to voltage drop.)
This happens if too small of a gauge of wire is used or there is a poor electrical connection.
I would make up a cigarette lighter plug in which is tied to a voltmeter. Then plug that into the cigarette lighter. Drive as normal and watch the voltage. Look at the voltage when the battery light comes on.
That is the "inside the vehicle voltage".
You can also string wires to the battery under the hood going to a voltmeter inside the car. Then do the same test.
You may find that the voltage at the battery is perfectly ok, but the voltage inside the car is dipping down???
If that is the case, the cause could be a poor body ground connection from the battery. Or a poor body ground connection for the gizmos in the dash. Or too small of a main wire being used to power the things inside the car and "voltage drop", poor connection, etc.
I'm just tossing this out to see if anyone happens to come up with something I have yet to think of....
Since the weather's gotten extremely hot on the East Coast, I've been having a completely random light-up of my battery warning lamp on the dash. It could be just a coincidence that the problem started when the weather changed??
It doesn't seem to be related to anything in particular and there's no pattern. It can go days without lighting and then come on for no apparent reason while motoring along. The car (2004 Jaguar X-type 3.0 AWD Automatic) lacks an amp gauge so all there is is the battery light to go on.
Turning off the ignition and restarting the car clears it and it might not come on again for another day or so. When the light is on, everything electric still functions normally. I've had the battery checked-out and a load test done on the alternator....everything checks out OK. I have yet to be able to check those though when the light is illuminated because it's so random.
I've checked the battery terminals, loosened, twisted, and then re-tightened them to be sure there's a good contact. No corrosion is present there either.
I've searched Jaguar forums and it seems to be fairly common. One guy drove with his battery light on for 90 days now. Others have been to the dealership, gotten new batteries, gotten new alternators, and even the dealerships don't seem able to correct it. It doesn't store a code either.
I know the jokes about Lucas Electrics and British cars, but this Jag has all Bosch or Ford components.
If it were mine, I would get to a walmart and buy a ciggy butt lighter voltmeter off the battery rack. It simply plugs in like this
see lower left with the greenish light is, and read voltage.
What I suspect is worn carbon brushes on the slip rings of the alternator, or perhaps a dirty brush holder, where crudlings create a path to ground.
If summer has anything to do with this, it might be more humidity and the crudlings are acting together and getting a weak charge to ground inside the alt case as well.
I'd be checking every one of the ground connectors and connections in this car.
The charge warning light circuit is triggering due to variations in the circuit voltage to the ECM.
You'll need to actually tear apart and clean every one of the connections. Additionally, it may be prudent to add more grounding wires between the alternator/chassis/ECM circuits. Many production cars don't have adequate or sufficient grounding circuits.
The only way you can ever locate this type of problem is with a voltage drop test under load at each ground location. It's simply easier to go through all the grounds and optomize them then it is to worry about which specific ground point(s) are the causation of the problem.
Proof that the alternator output and battery condition is not the issue is having had them load tested and getting an OK result there along with the continued normal functionality of the electrical/electronics of the car while the charge warning light is on. The fact that the light "resets" with cycling the ignition on and off is another clue that this is a voltage spike or drop issue ....
Many voltage regulators have a thermistor to control charging.
During warm weather it is easier for the chemicals to flow in the battery....thus making it easier for the battery to be charged. The thermistor will sense warmer weather and turn the field current on later/less often to compensate for the ease of charging(and to prevent overcharging) in warmer weather.
If this problem is not effecting operation of the vehicle in any way, I would not sweat it.
The battery voltage should be 12.6 volts when turned off......plus float charge of .1 to .4 volts. Normal drain current over time will take your battery down (depending on how good your charging system/battery is, how long the car sits not running) to below 12.6 volts.
With the car running you should see charging voltage between 13.5 and 14.5 volts(some charge higher).
Jag's spec for a warm battery, warm engine, hot day is 13.2 to 14.3 volts. On cold days, it may charge as high as 15.1 v.
The charge warning light in this car is not triggered by an older warning light system where the alt output voltage is less than the battery voltage. The charge warning light is triggered by the ECM, and a no-charge condition will set a DTC fault code.
The service manual is very specific that if the ECM senses a "no charge" condition, it will trigger the warning light on the dash. With a 130 amp alternator and the electrical consumers on this car, the alternator must be putting out a fair amount of amperage to run the vehicle systems and keep the battery charged up, which appears to be the case in this thread per the OP.
It would be nice if the service manual went into a bit more technical detail as to specifically how it determines a "no charge" condition!
These new cars are getting to be quite complex. It is a BIG help if a tech can fully understand how various things work.
They do this in the rest of the electronics world - provide schematics or very detailed descriptions of operation. But the automotive world keeps the internal workings of ECM's and the like a secret.
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