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Cheshire Dave

Member Since: 05 Jun 2014
Location: Chester
Posts: 119

Battery warning light

When idling after a few mile journey the battery warning light pulses on and off, goes out if you increase the revs though but when pulsing there seems to be a different engine sound. Any ideas, is this a potential problem looming. Or am I being paranoid ?

Dave
110 300tdi

10th Apr 2015 9:45pm

munch90

Member Since: 26 Oct 2013
Location: guildford
Posts: 3558

You say engine sounds different, is it ticking over slower ?

10th Apr 2015 9:48pm

K9F

Member Since: 12 Nov 2009
Location: Bournemouth
Posts: 9610

2008 Defender 90 Puma 2.4 XS CSW Stornoway Grey

Under fault conditions measure the output of the alternator with a multimeter, it should be ballpark 14 volts. Once running a diesel obviously doesn't need a battery to keep running, if you have the technical accumen you could also carefully disconnect the battery positive and measure the voltage on the vehicle terminals to see if your battery may be shot and is dragging the alternator output down, or if you have a spare battery (or perhaps 'borrow' one from another vehicle) chuck that in. If you go through life with your head in the sand....all people will see is an ar5e!!

Treat every day as if it is your last....one day you will be right!!

10th Apr 2015 10:35pm

Cheshire Dave

Member Since: 05 Jun 2014
Location: Chester
Posts: 119

Thanks guys I'll get it checked out, battery was ok late last year and hasn't been checked since.

11th Apr 2015 6:24am

mikeh501

Member Since: 07 Jan 2013
Location: United Kingdom
Posts: 1142

K9F wrote:
Under fault conditions measure the output of the alternator with a multimeter, it should be ballpark 14 volts. Once running a diesel obviously doesn't need a battery to keep running, if you have the technical accumen you could also carefully disconnect the battery positive and measure the voltage on the vehicle terminals to see if your battery may be shot and is dragging the alternator output down, or if you have a spare battery (or perhaps 'borrow' one from another vehicle) chuck that in.

I found to my cost that isn't exactly true. Even on my old TDI unit the diesel stop solenoid is electrically operated in that the voltage keeps it open. Once the battery is fully goosed then it drops back and cuts off fuel from the engine. I'd guess the later engines are even more reliant. Took 3 days to happen like

I wondered why my wipers were slower than normal lol

11th Apr 2015 6:34am

munch90

Member Since: 26 Oct 2013
Location: guildford
Posts: 3558

could really be a few different things

tick over speed dropping causing alternator to spin to lower rpm that can make light flicker also different engine noise

belt slipping

diode in alternator , will still charge but at lower rate

as said check voltage on tick over and revving a bit and with headlights on to load alternator a bit

dodgy battery wont normally put alternator light on , unless its really knackered then defender shouldn't start at all on the battery

11th Apr 2015 7:43am

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