I have just fitted a new alternator after my old one bit the dust. The new one is identical to the old one so I had no trouble fitting it, however
despite charging well (showing 12.6V with all lights on, engine running, radio and heater full blast) the charging light on the dash is switched
on.
Is there any reason this could happen, bearing in mind I haven't changed anything electrical? Is there a part of the new alternator that can
malfunction like this?
Depends on the alternator. A lot of the denso ones need a transistor wired in to get it to go off.
I would expect your voltage to be more like 13.5v though. Turn everything off and try again!
Mine is charging fine and the light stays on. So I reconfigured a programmable light on the dash to show me if there was actually a problem and now
just ignore the battery light! 
Maybe I will cover it at some point.
It is a Denso (or looks like one anyway) and is identical to the old one in every detail. Not sure about your transistor but my warning light is just
the normal affair with power from alternator and battery to either side of the warning light (LED in my case) I never had this problem with the old
alternator so it is a bit puzzling.
I am getting 13.2V with everything switched off (with engine running) so I reckon it is ok in that respect - I think I will email the supplier and see
what he says
12.6 with all on and 13.2 with all off is low. I would expect more like 14.5 v. Denso alternators can need two wires apart from the big one to the
battery. An ignition live for excitation as well as the ignition warning dash light wire.
Just seen you have an LED warning light. That introduces polarity possibilities etc.
[Edited on 12/5/10 by Dusty]
My Denso alternator outputs a signal to the warning light, so with it wired as you have described the light would probably stay on.
They aren't all the same though.
I wired mine so that the signal the alternator ouptuts when not running switches a transistor that in turn switches power on to the warning light.
When running there is no signal so the warning light goes off.
Check if the alternator can light up and lamp from the warning light output. If it can't, but is still putting out a voltate, then it is the same
as mine
Stu
quote:
Originally posted by Dusty
12.6 with all on and 13.2 with all off is low. I would expect more like 14.5 v. Denso alternators can need two wires apart from the big one to the battery. An ignition live for excitation as well as the ignition warning dash light wire.
Just seen you have an LED warning light. That introduces polarity possibilities etc.
Update: I have just had a reply from the supplier saying that he doesn't think the alternator is faulty (well he would wouldn't he ) but
accepted that if I wanted to return it for a refund that was ok.
My warning LED is actually part of my Evodash which has worked perfectly until I changed the alternator. I am reluctant to start ripping my loom apart
to change it - much better to find a suitable alternator IMO. Having said that, the voltage readings do seem a bit low so I might swap back to the old
alternator (bearings are shot but electrically it's ok) and recheck at the weekend.
Just a thought - is it possible to swap the regulator pack (or whatever controls the warning lamp) from the old to the new one easily? It might be a
solution if they are different somehow.
[Edited on 12-5-10 by RazMan]
Why not just order a pair of bearings?
Davie
i'm with the supplier - low probability of new altern ator being fault.
take a look here - see if you can identify the regulator.
it appear the pins are labelled - my money is that you have same plug but different wiring.
in theory they should be direct replacement (a sensble design) - no idea if they are since I never took one apart but from the pictures, they look
like bolt in replacement.
http://www.fae.co.za/Web%20Catalogue%20Pdf/Regulators/Nippondenso%20Regulators.pdf
[Edited on 12/5/10 by 02GF74]
quote:
Originally posted by 02GF74
it appear the pins are labelled - my money is that you have same plug but different wiring.
quote:
Originally posted by daviep
Why not just order a pair of bearings?
Davie
Actually the casing looks like it took a hit from something which is possibly why the bearings went. This way I should
get a new alternator for £25 :cool Update:.... I have now sorted the problem and it was definitely the regulator pack that was the culprit. Both old and new ones were identical but with
different part numbers so it appears that they must be electrically different in some way. It would be nice to figure out exactly what the difference
is - it might be the transistor that Flak mentioned - either way it is sorted 