Battery light on but alternator working fine

[adam quantrill]

Hi the battery light came on the other day although the volts were fine (lights on too) and that was confirmed with a voltmeter on the battery terminals.

Alternator swapped and the same results. It's not the fan belt either.

I vaguely recall something like this happening before and it was a fuse or something connecting to a related circuit, but can't remember what, will have to do a search.

[adam quantrill]

Yeah this is full on irrespective of engine speed.

[adam quantrill]

Yeah it does.

Full symptoms are:

ignition off - light is off, battery does not go flat overnight.
ignition on - light comes on
cranking - light goes off
running - light comes on
turn off ignition - light goes off quite rapidly

The fault I was thinking about on the other car was to do with the full beam somehow - as I recall the full beam warning light was lit dimly. In this case, it isn't.

I don't think there's any fuse in the alternator circuit at all, on a wedge. Battery side or field side.

[adam quantrill]

Gauges are all working so it's not the fuse (apart from the clock but that hasn't worked for 7 years....)

I can try the turn over test but the same symptoms were present with another alternator and I specifically checked the brushes on this one anyway before fitting it.

[adam quantrill]

You are right though it might have been fuse 13 previously, and there's a path through the main beam warning lamp for the alternator field to get a bit of juice, so it glows dim.

Having said that, that was a different car and maybe this one would present a different symptom, so worth checking the fuse.

Edited by adam quantrill on Monday 27th November 21:03

[adam quantrill]

Have just checked all the fuses, all OK, cleaned up a few of the blades.

Still have the same symptoms. At least it's charging OK.

[adam quantrill]

Update on this - I had a brainwave when replying to the other alternator post...

I hadn't connected up the correct "sense" post on the new alternator, connected it up just now after removing my "blade" adapter (the other alternator had blade connectors for the sense connector).

Normal service is now resumed, charging at 14.4V. Battery topped up too.

[adam quantrill]

Yes - I never look at the speedo anyway! ;^)