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Old 25th June 2021, 17:41   #1
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Default Battery light

Hi all. Having issues with battery waring light it keeps flikering and stays on ive gone over the earths fitted a new battery and alternator with no success i am out of ideas now and hope someone could think of anything to look at thanks. 1.8 petrol

Last edited by rover_ed; 25th June 2021 at 17:57..
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Old 25th June 2021, 17:49   #2
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Hi all. Having issues with battery waring light it keeps flikering and stays on ive gone over the earths fitted a new battery and alternator with no success i am out of ideas now and hope someone could think of anything to look at thanks
You're not alone, mines doing the same after an alternator change, it's charging fine but battery light is glowing all the time. I'm led to believe that there is some wiring that can change through round by the washer bottle area, it's a bumper off job to check, bumper off is a simple job but I always struggle getting it back on so I've not bothered too much.

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Old 25th June 2021, 17:53   #3
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I did have bumper off a not so long back and couldn't see any problems with any wires but could of missed somthing
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Old 27th June 2021, 10:49   #4
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Hi all. Having issues with battery warning light; it keeps flickering and stays on. I've gone over the earths, fitted a new battery and alternator with no success. I am out of ideas now and hope someone could think of anything to look at. Thanks. 1.8 petrol
The pic below might help.

A poor connection from either the ignition switch or the alternator to the warning light.




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File Type: jpg Alternator..jpg (66.8 KB, 34 views)

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Old 27th June 2021, 11:32   #5
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How does a battery warning light work, very simply.


It serves two functions, the main one being to allow a small current to the alt to start charging at low revs, the second is that it acts as a charge warning light.



Engine stationary, ignition on, the battery + current say 12v flows through the bulb and to bat - 0v through the alt, via the brushes and slip rings, a difference of 12v from one side of the bulb filament to the other, so it lights up.


Start the engine and the alt starts to charge at say 14v, this voltage is now present at both the battery + , ignition switch and ignition switch side of the bulb and also at the alternator side of the bulb, 14v at one side of the filament and 14v at the other side of the filament, the bulb won't light.


So what can cause the bulb to come on and, or flicker ?


Dead simple in theory, anything in any circuit from battery +, to ing. switch, to bulb, to wiring, to multi-plugs to alternator internals, to bat -, where there is is a poor resistive or loose connection and causes a volt drop across that connection of say 1v or more.


We than have a difference in voltage between either side of the filament and depending on what the difference or cause is, it will cause the filament to glow, flicker or stay on even though the alt is charging perfectly.


So in theory, somewhere, there is simply something causing a volt drop on one side of the bulb or the other, the practical side, finding the fault isn't that simple though.


There will be many an alt. replaced unnecessarily due to the above.
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Old 28th June 2021, 19:20   #6
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Old 28th June 2021, 19:26   #7
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Thanks for the replies i will be having a look during the week after work have a good look over the loom battery wires and from the alternator if im sat at idle very rarely come on mainly as the revs are raised
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Old 28th June 2021, 19:31   #8
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My reply could be better but 2 kids running round and playing a banana game keeps throwing me of took me half hour to write that
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Old 29th June 2021, 09:22   #9
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... if im sat at idle very rarely come on mainly as the revs are raised
Thanks for this little gem Ed, it's very unusual and the opposite of what usually happens.

How's the alternator drivebelt tension? Do you hear any squealing?

Have you activated the instrument pack diagnostics to monitor the charging voltage? It would be helpful to know what this is as the revs are raised.

Simon
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Old 30th June 2021, 16:11   #10
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The volts on the instrument panel is 12.4 idle and reved or driving is 14.2
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