Battery Warning Light

Hi all,

Hope everyone is well?!

Just had a strange issue with the battery warning light.

Driving home from the office (50 miles in a diesel series 3!!) I noticed the battery warning light came on dimly while I was braking. I tried the lights the warning light flashed then went off. Then all was OK with the warning light. Well, for a few miles.

The warning light came on again again with the brake light, and flashed with the indicator, and came on full with the lights on.

I made it home, and have just started it again (started with no issues). The battery reads 13.5-14V with the engine running. I can put the brake on and the voltage drops a tiny amount but the battery is still charging!

Any ideas?

At the weekend I changed the brake flexible hoses, and noticed that the cables running to the rear are actually house wiring 1.5mm cable!! I'm guessing that anyone that has done that could've bodged up something else so I'm certainly going to re-wire the rear half of the vehicle at least.

Cheers,

Bern.

The light could be coming on of you've got a bad earth somewhere.
Suggest you start by putting some decent wiring in place of domestic wiring then check what else has been bodged. Connections could be old and corroded etc

Look/ensure a good engine earth.
Then go behind the clocks & check the earths there.
As for a re wire, 7core cable to the rear & its an easy job

kermit_rr said:

The light could be coming on of you've got a bad earth somewhere.
Suggest you start by putting some decent wiring in place of domestic wiring then check what else has been bodged. Connections could be old and corroded etc

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As well as updated/correcting your wiring to the back, check the thin wire from the alternator to the warning lamp (it should be brown with a yellow trace but if the front end wiring is anything like your rear end wiring it could be any colour!), if its frayed or chaffed and its rubbing on the engine/bodywork (possibly while braking) then it'll earth and light up.

Start saving for a new alternator.

Col

Colthebrummie said:

Start saving for a new alternator.

Col

Click to expand...

That said, you can buy all the parts to service an alternator, if you are that way inclined.

Wow, thanks all!

The alternator is less than 18 months old, though that's no guarantee that it's OK.

I will re-wire the rear, check the earths and see what else needs doing.

+1 on checking for loose or corroded connnections. From the symptoms you describe, I'd check the main feed (brown wire) from the starter motor to the ignition switch, but that assumes the wiring is more or less original and it sounds like a previous owner has bodged it... Good luck!

Hi. I followed some advice, probably on here, that said you can never have enough earths and before doing any wiring practice the fine art of crimping. I put a light on the tailgate of my 72 S3 to act as a reverse light and added the switch to the dash board. Going behind the dash revealed all manner of bodges so I practiced and replaced anything that looked iffy. If I can do it then it is very doable. I also regularly clean all contacts to the bodywork and terminals. Ah the smell of contact cleaner from an aerosol. Somebody should turn it into a shower gel. Good luck with the wiring.