david r simpson wrote:
>
> I have just replace the alernator on a 1976 spitfire, after a couple of
> years of non-use. Now the ignition warning light only comes on when the
> alterntor is putting out 14 volts, it is off with the ignition on and the
> car not running and then comes on after the car is running. I assume that
> the signal for the light comes from the small brown & yellow wire from the
> voltage regulator inside the alternator. Any thoughts or good trouble
> shooting manual that explain how these system work. Tanks Dave Simpson
>
> 61TR3
> 76 Spitfire
> 91 Ford Explorer
> British Sea Kayak
David,
The indicator light only comes on when there's an voltage imbalance
(different potentials at the bulb terminals) between what the alternator
puts out and what's available to the harness. Yes, the brown/yellow wire
from the alternator connection goes to the IGN bulb in the speedo. The
Lucas regulator is set to limit voltage between 13.5 and 14.2 volts. What
you describe indicates there's more voltage available from the alternator
than there's available from the harness--a really unusual situation.
Check the voltage between the battery terminals, with the engine running,
and no accessories on. You should have a voltage reading within the
13.5-14.2 range. If that voltage is correct, the alternator is
charging--your problem is in the harness; i.e. high resistance between
the battery and the IGN bulb.
A good digital VOM is helpful here.
Charlie B.
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