Where is the charging light source voltage(dashboard indication of no charge from the alternator) derived from. Is it an indication of a changeover within the regulator in the alternator or something else?
It gets 12 v from an ignition switch live then goes via the bulb to the warning light connection on the alternator. I beleive it works something like
this.
Ignition on, bulb gets 12 v from ignition switch and earths through alternator.
Once engine is started, the alternator gets exitation from the 12v via bulb, then starts producing volts.
Once the volts reach the same as coming from ignition switch to bulb, the bulb dims and goes out, you have chargeing !!
It's something like that but the supply definately comes from the ignition via bulb to warning light connection on alternator.
hope this helps
That sound logical, the loom I am using is from the Lancia and the igition light was part of the console which monitors all services and lights. So
when I threw that away I lost all reference to where this connection came from and didn't consider it until this weekend when I was sorting out
the dashboard displays.
It should be a straightforward task to wire one in although with all the indicators my dash will look like Blackpool at Christmas.
Take a look at my dash lit up on my photo archive, looks simple but the wiring is still a nightmare behind the dash !!
I can imagine, but it looks good. Mine is not only Italian wiring it is also hooked up to Ford column switches, the Lancia didn't use relays for
the headlights etc but fed all the current through the column switches. The Ford switches would melt so I have had to modify the loom to incorporate
relays for lights.
It is like playing chess with electrons!
does this mean that the charging light is needed to set the altenator off? i always assumed it just tried to earth thru the alternator, and couldnt when it was charging. hence no light when charging.
what fifer said is right,ps you wouldnt happen to have the sun roof relay from the lancia would you?
On my alternator - bosch I think - it absolutely needed the bulb in circuit, or it didnt work.
Nice one that in real life. Bulb fails - not only does it stop you from knowing if the alternator fails, it ACTUALLY MAKES IT FAIL!!!!
atb
steve
quote:
Originally posted by JoelP
does this mean that the charging light is needed to set the altenator off? i always assumed it just tried to earth thru the alternator, and couldnt when it was charging. hence no light when charging.
quote:
ps you wouldnt happen to have the sun roof relay from the lancia would you?
Back to the charging question.
As the charging light requires a + feed to the bulb and when the alternator produces a charge it cancels out the circuit. Will this have to be a
dedicated + feed or could I use one that feeds other services on the dash? My concers are that the other circuits (which have their own earths) may
then provide an earth for the charging light circuit.
Not 100% sure but on mine, the supply comes from the ignition (white on my loom) but it also supplies the oil pressure warning light bulb / switch.
best bet would be to run a supply from your ignition switch position two, that way, you know it will work.
nick,the relay is £50
from fiats,its for my alfa 155,as long as the feed to alt goes from sw---bulb---alt it will work,use the right wattage bulb
tho
I don't think the relay is something I will have from the Lancia loom but I will look tonight. I think the wiring diagram shows a rook relay.
just connect the lamp to a switched positive supply - there are no tricks or earthing paths to worry about.
Just make sure its fused, so your suggestion of wiring it to the normal dashboard lamps, or dash instrumet supplies, will be fine.
atb
steve
Thanks for the replies, now I need to just get anothe light to connect it to.
Don't mean to confuse people here, as I am far from certain of this, but what Fifer said certainly was the case with older alternators, but I ma
not so sure now.
The bosch one on my Vaxuhall 16v (from 1991 Cav 16v) does NOT need the warning light wire connected in order to charge properly. It is still
connnected to an ignition switched 12v feed just the same, but the wire broke at the crimp ring where it connects to the alternator (years ago when
the engine was in my manta) and I drove it for ages with no connection like this (only half noticed that the charge light wasn't coming on when i
put the ign on without the car running)
I think there must be a transistor switch in the alternator which just earths the 12v warning light feed until the alternator is charging
properly??
Certainly what Fifer said used to be the case, all the tractors at the farm and our old lorries used to show a dying alternator with a faint glow from
the light, but I think maybe this has changed now.
( I was having pretty much this conversation with a electronics engineer friend of mine yesterday because I want to use an LED for my charge warning,
which will not work if Fifer is correct (and I hasten to add as I previously thought) as it will not take back-voltage. However if the alternator just
switches to earth as I now suspect then there will be no problem)