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Richard, Jaguar Technician
Category: Jaguar
Satisfied Customers: 15307
Experience:  12 years at a Ford/Lincoln Mercury and Jaguar dealer as technician and shop foreman.
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Jaguar 2005: My battery Warning light keeps appearing and disappearing

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My battery Warning light keeps appearing and disappearing. Its like a programming BUG or Ghost but the car runs fine.

I have read forums, and this is very common.

The alternator and cables were changed. The Jaguar Dealership says the battery is fine and the car checks out as OK.

One "Forum User" say: the heated cables cause less voltage flow hence, triggering the light. This is true in electronics and electronic circuits period but, car cables are made to take heat I guess????

Hello and welcome to

Is this a X type model? Can I have the last six digits of your VIN? Were both the positive and negative cables replaced?
Customer: replied 3 years ago.

this is the x-type 05




Both cables replace in 2008. This is not a new short of some kind.


The Jaguar Dealer did not find any issues with this car. As stated, I see others with this complaint in forums.

Ok I am wondering if there is a poor connection with one of those cables or there is a problem with the wire harness from the alternator to the ECM. We also need to monitor the output when the warning is on at the battery with a digital meter. We need to check this when the warning light comes on. we can put the instrument cluster in engineering mode to see what voltage the cluster and ECM are seeing. First turn off the engine. Press and hold the trip button in the turn signal stalk then start the engine while holding the trip button. You will see the instrument cluster go into engineering test mode. Release the trip button then keep pressing it until the voltage reads a digital number.
Customer: replied 3 years ago.

I did that what you wrote, it goes into test, the gauges go crazy and I press trip again;


the red and yellow lights come on and all i see is A:720.2 and below the mileage i think


please help me to do the procedure correctly or know when the number appears.

Keep pressing trip in this mode and it will display the battery voltage.
Customer: replied 3 years ago.
It seems like a common sense procedure. As a regular I can follow 3 or 4 steps but, it doesn't display a voltage Step 1) hold buttonStep 2) start engine Step 3) car goes into test, release button Step4) hold trip button until a voltage appears. Didn't see it
Dont hold trip but keep pressing and releasing as it will show numerous values. Stop pressing when you get to voltage.
Customer: replied 3 years ago.
Bat started at 14.7 initially and it swung to 12.8
IDV 00
AC 0

It steady stayed at 12.9 there after.
Ok compare that reading to a voltage measurement at the battery with a digital multimeter. You may see about a w volt difference.
Customer: replied 3 years ago.
I'm a lay person.

I checked the battery voltage after my drive to work and it read 14.7, up from the 12.8 last night. This reading was my inital reading ( 14.7), when you first instructed me to check.

So clearly it either has different level or it is fluctuating in output.

Is this common, as I can see a spike causing the light to activate? Suggest a good TECH and location in NJ who you know will solve this?

Can it be solved?? Lol
I first recommend using a digital meter to check the battery voltage. With the engine running and all accessories off we usually see around 15 volts which means a good charging system. Then start turning accessories on like lights climate control and defogger. The voltage should stay near 14. If you do not have access to a digital multimeter most parts stores can do this testing for you.
Customer: replied 3 years ago.
Keep going, I do have plenty access to a DMM

I probably will not get 15 V, it seems 14.7 is my official max voltage.

ANYWAY, following your instruction;

After each unit ( radio, AC etc) is on, if there is a dip in Voltage, what's the next step??
I suspect a dip will happen.

Any luck on suggestion for a knowledgable TECH in the NJ area?
Honestly it is very hard to find good Jag techs anywhere unless you go to the dealer. Yes you will see a dip in voltage. Start the engine and set your meter to dc volts. Place the red lead to the positive terminal and the black lead to the negative terminal. You should see 15 volts. Then with all accessories on you should see around 13.5. If you have this then everything is working. We will need to perform this test again when the warning comes on to see what the exact voltage is.
Richard and 3 other Jaguar Specialists are ready to help you
Customer: replied 3 years ago.
I failed to mention the light goes and comes.

You see it come on, turn the car off then on sometimes, and it clears.

Its not constant but, a predictable expectation.

I will do the electrical test and state my finding.

Customer: replied 3 years ago.
I tested the voltage using a DMM

On start up I saw 15.2

With all loads ( lights, AC, Radio etc), I saw 14.5
Ok those readings indicate a good system. We need to perform the same test when the light comes on.
Customer: replied 3 years ago.
The weather has been consistently cool in NJ, I suspect my battery light issue is heat related.

Last week when temperatures were high two days in a row it came on.

What's your interpretation?
I am thinking it could be an alternator problem which can definitely be effected by temperature. I still do not want to rule out a cable problem.
Customer: replied 3 years ago.
The alternator was replaced
I am thinking it could be defective.

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