[DML] Re: Alternator Light - question

["content22207" <brobertson@xxxxxxxxxxxx>]

Correct. That's why you should glance for the dash light to come on
when the car is first energized.

The dash light is a failure alert mechanism (as well as the exciter
for the field). When the alternator is not spinning, the light bulb
uses field wiring as its path to ground and glows at maximum
intensity.  As the alternator comes up to speed, 12 volts gradually
builds in the field, the dash light gets dimmer and dimmer, until
"eventually" (it actually happens quite quickly) there is 12 volts on
either side of the bulb and it stops glowing altogether. The
alternator is now producing at least the same voltage as the battery
and all is right with the world.

If something goes wrong with the alternator field (which can be as
simple as a broken drive belt), voltage in it will drop and the dash
light will start to glow again.

Before I get flamed: "12 volts" is general nomenclature. Good battery
voltage is actually 12.5 to 12.9 volts, and charging voltage is 13.8
to 14.5 volts.

Bill Robertson
#5939 

>--- In dmcnews@xxxxxxxxxxxxxxx, "daviddelorean" <daviddelorean@...>
wrote:
>
> I'm a little bit corn-fused. Why not just have a direct line from the 
> ignition / + terminal of battery go to the alternator to give it juice 
> to start making electricity? Why do you need a light bulb in the line? 
> I don't understand what exactly the bulb itself does. So if I 
> physically remove the light bulb from my binnacle, my alternator will 
> be spinning but not generating electricty?
> 




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