Battery Light Advice

0writer · Sep 29, 2012

Afternoon all,

The battery light is lit up on my dash, nice and bright.

I needed a new battery anyway so that has been replaced in the last week but the light was still on. I knew the tensioner bearing needed doing so have done that today along with fitting a new belt but the light is still on. I get 12.5v when off and 14.7v when running across the battery.

Any ideas?

blue beasty · Sep 29, 2012

Warning light wire connection on the back of the alternator. The light only goes out when the voltage from this wire is more than the battery voltage.

0writer · Sep 29, 2012

Thanks for the quick reply, sounds like I need to check the wiring is clean and tight at the back of the alternator.

ruffday · Sep 29, 2012

I could be wrong but 14.7v sounds a bit high to me.
Could be overcharging.

Freediscoranger · Sep 29, 2012

charging system should produce 14.2V +- 0.2 V

alex8882 · Sep 30, 2012

my alty normally puts out around 14.4v when charging

0writer · Sep 30, 2012

Just double checked the numbers to be sure and the voltmeter is showing 12.46v not running and 14.78 running which does seem to high. Any other advice or should I buy a new alternator? When buying, does brand make a difference? Was thinking off going 100amp.

discool · Sep 30, 2012

0writer said:
Just double checked the numbers to be sure and the voltmeter is showing 12.46v not running and 14.78 running which does seem to high. Any other advice or should I buy a new alternator? When buying, does brand make a difference? Was thinking off going 100amp.

Don't worry about the standby voltage only the max when charging via the alternator is 14.4v.
As u can see on my meter my battey voltage was just 11.7v when I took the photo, and this meter is certified every year which states it has 2% +- variability so it's doubtfull at 14.4v if it would read that.
So much for a £220 multimeter.

0writer · Oct 6, 2012

Got the alternator off the car today and my neighbour saw me. He said that if it's overcharging it could be the regulator on the alternator and it's worth testing that as it's £10 to replace. Does anyone know how i can test the regulator?

discool · Oct 6, 2012

You could have done a Google search on that.
Alternator & Charging System Checks (Alternator Testing)

0writer · Oct 6, 2012

But then I couldn't have thanked you for a great link (sorry, didn't think).

Thanks!

discool · Oct 6, 2012

0writer said:
But then I couldn't have thanked you for a great link (sorry, didn't think).

Thanks!

.... loads of info on that subject on the www and yes the diode pack is replacable but the wiring connections are fusion welded not screw, so you will have to cut and then use grimps not solder as that will/may melt with the high current, again, all info on the web :tea:

Battery Light Advice

0writer

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blue beasty

Leaks an prone to bits dropping off

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ruffday

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alex8882

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