6 replies to this topic

[alsy]

Hi... soooooooo, my battery was dead, jumped it.. drove around for near on 3 hours to charge it.. it started up this morning.... just. then I left it running for a bit with the lights on and I noticed them dimming.. then the car turnt off and had no battery again. am I right in saying this is down to a broken alternator and can someone please link me the best one for my mini :)

mini 1000 - 1975.

Thanks.

[newnham500]

could be down to the bat, or you could have something leaking voltage (draining the bat). do you have a multimeter?

[alsy]

No I don't..

[Barman]

A multimeter is cheap (~£12) and will tell you if the problems is with your battery, a leak, or the charging circuit....

[chrisandsarah]

Checked that the leads are attached to the battery + tight enough...

[Cooperman]

Check the battery leads and the earth connection from battery to boot floor and from engine block to body.
If that is not the problem it may well be the battery. Poor batteries do show up in colder weather.
Check the fan belt tension.
It's unlikely to be the alternator unless the ignition/charge warning light is on all the time, or at least glowing weakly.

[tiger99]

The battery went down with the engine running, so it points to alternator, although the battery itself may well be dying too. First thing to check is that the alternator warning light comes on with the ignition, and goes off when the engine starts. A failed bulb will deprive the alternator of its initial excitation, so it will not charge, even if perfectly good. Light on when running of course means that the alternator is dead or something like a slipping fan belt is preventing it from being driven, although a slipping belt would be obvious in other ways.

If the warning light is ok, I would do all the simple stuff, like removing, cleaning, greasing with vaseline (nothing else!) and refitting the battery and engine earth straps and the battery positive terminal, before spending any money on a new alternator. These things most likely need attention anyway, they always do after a while.

Then it is worth getting a multimeter. Engine running at moderate revs, battery should get to over 13.8V, and should eventually reach about 14.4V when fully charged. If it does not get to at least 13.8, the alternator is faulty.

Simple battery test. Charge fully, then headlights on, engine not running. The lights should be good for two to three hours depending on which size of battery and which light bulbs are fitted. If it achieves at least an hour, recharge it and it will do for a while yet, but will need replacing soon. Less than an hour, replace it now.