I hope your system is nothing like my SAAB (Bosch?). I made the mistake
of
changing all of the dash lights just because I had one out and had it apart.
The charge light MUST be the correct one or the circuit will not get enough
current to charge properly. The proper replacement bulb was $8! (Then I had
to change the alt. brushes a month later.) In most systems I have seen the
bulb lights (verb) because of the current going through it due to the field
current level. If they are directly related in the above fashion you will
have to add a bypass resistor as well, its value will decide the maximum
charge rate (too low resistance may let it charge at a higher current than the
alternator is rated for and things may fry). The best thing is to leave the
circuit original and add the LED in parallel (to the original bulb) using the
proper value resistor or HIGHER to get the desired results. You don't want it
dimly lit all the time if things are otherwise OK. Use the suggested value
and add a potentiometer (pot) in series, when things are stable it is to be
varied such that the LED just goes 'out'. Just because it is dim after that
doesn't mean anything is wrong, just working (high charge after startup). If
it stays on . . . Use it with the standard setup until you know
what to
expect. Later on you can change the bulb to a resistor after using an ammeter
and voltmeter and factoring the proper resistance required. Just remember
that the resistance goes UP as the filament begins to glow. You sometimes
can't just replace a bulb with an LED. Some old style turnsignal flashers
will quit or flicker (mayby not yours, but my plane will need them). I hope
this book doesn't scare anyone too bad but a little fear is a good thing, it
keeps us from doing something dumb (sometimes). (Corrections/comments
accepted)
Dave Faust
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