Sat, 29 Mar 1997, 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
Dave:
Usually, this means you have a bad Battery. When you turn on the key, the
battery provides power through the lamp to the alternator, which is not
producing power. This also suplies a small field voltage to "kick start" the
alternator. Once the engine is running and the alternator is producing, equal
voltage (or very near equal) is present on both sides of the lamp, so it is
not lit. Power to drive the lamp from the alternator comes from a separate
set of diodes, just like the main diodes which provide charging current.
After the alternator is producing, these same diodes provide the field
current to the alternator.
Are you starting the car from it's own battery, or jump starting it? If your
battery is good, and the Spitfire is wired like a TR6, I can only see one
possibility. The Brown/Yellow wire goes from the alternator to the lamp, and
a White wire goes from the lamp to the run position of the ignition switch.
Since the rest of the car is working, the ignition switch is good, so the
white wire from the lamp must be off, and touching ground somewhere. I don't
have a Spitfire schematic, so I can only guess that it is like a TR6 - any
one care to donate a xerox copy to me? Power to drive the lamp from the
alternator comes from a separate set of diodes, just like the main diodes
which provide charging current.
Dan Masters,
Alcoa, TN
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