battery light

[Mickey taker]

battery light has come on today and stayed on ,
whats most likely , alternator or regulator?
I have a spare valeo alternator but not sure if its any good yet.
is it worth taking the regulator pack off the one on the car and checking the brushes?,
I also have a spare regulator pack but one brush looks a bit worn down

[themildbunch]

If you have a meter you could check the voltage across the battery terminals when the engine's running but more than likely the alternator's gone...

My TZD did this recently but the battery light flickered and gradually the battery would drain - one of the brushes in the Alternator had totally worn out - got the new part with new brushes for about £10 - I had to take the alternator to the auto electrical place as it was such an old part! Much cheaper than a new alternator though - If you take yours off you can check the condition of the bearings too - if they're good I'd just replace the brushes first.

[Mothman]

Deffo the alternator bud, happened to me twice last year and i now carry a spare for long journeys plus the batt charger. Gofor the simple and obvious things first, usualy the right decision as they dont last forever. My alternator lasted 6 years on the NA diesel so cant complain. Now have several spares but plenty can be sourced on feebay.
An easy fix but the bolt can be a bugger to undo, snapped it on the scrapper.Did test it first at my local garage and it was showing 11.6 volts which was obviously a problem.

Andy

[Mickey taker]

the spare is a 50amp valeo which is the same as whats on the car so I think I will swap them then get the brushes done on the one I take off the car making that a new spare

[electrokid]

Or the alternator belt...

[Mickey taker]

alternator belt seems quite new and tight

[Vanny]

Did you put a meter across the battery yet? If your exciter has a poor connection (usually in the multi connector that goes through the bulk head, over the gearbox) then you can change the alternator as many times as you like but it wont help. I killed a few alternators by not caring for the excitation of the alternator.

[Mothman]

Bet its the alternator!!

[Mickey taker]

light go's out with revs and comes back on when cruising.
interested to know more about this exciter thingy though Vanny

[Mothman]

Get the alternator tested at a local garage bud and you will have a very quick answer. Noneed to pontifitate further.Still bet its a knackered alternator.

Andy

[electrokid]

light go's out with revs and comes back on when cruising.

Inside the alternator there's a brush, sometimes two, that connects to a slipring on the rotor. The brush can wear to the point where the pressure spring that normally pushes it onto the slipring runs out of travel. High engine speed can jiggle the brush so it makes intermittent contact with the slipring and make it appear to charge enough to extinguish the light though the actual amount of charge achieved could be very small.

[Mickey taker]

what size is the big nut ?

[Vanny]

22mm i think, possibly 19, but it has a torque drive in the end which is t30 to t40. you can slack it off with an adjustable spanner and then undo by hand.

[docchevron]

21MM

[Mickey taker]

removed alternator and took off regulator pack to find one brush pretty low and the other one slightly better so have replaced them, would still like to know more about this exciter though