alternator charging again

INCase · Apr 18, 2014

have tried a few things to get the alternator on the 9N to charge. If you jump it from the #1 terminal to the pos post on the alternator it will charge.

The idiot light I've got is a generic red napa one. I put a regular clearance light in the circuit too (like some have suggested) and it still will not work. If i go direct to the ignition switch it will charge (checked with putting meter on battery showing 14v).

So i'll go with the diode. What size diode should i use? will probably go to radio shack to get it.

Thanks.

Janicholson · Apr 18, 2014

Adding additional lights together in parallel is different than adding them in series. In series the resistances add together making a low resistance filament even less effective at supplying volts to excite the alt. In parallel, the resistance is decreased, making the voltage supplied greater. If you put the parking lamp in series with the other indicator, (try attaching across the other light.) it might work. A diode must also be placed across the indicator lamp you already have ot it will not work either. Nothing goes to ground, they are just parallel to each other. (Band on the diode goes toward the alternator). Jim

JMOR · Apr 18, 2014

When GM designed it, they used a 10 Ohm, 6 Watt resistor in parallel with the lamp. Why not do it the way it was designed? :idea:

Pappy · Apr 18, 2014

"OLD", when he posted here, recommended a diode from Radio Shack, Number 276-1661. He used to say that it was probably overkill, but had served him well.
I bought a couple but have not used them yet. Very inexpensive.

John T · Apr 19, 2014

I sometimes used a 5 or 10 ohm 5 watt resistor, that's more wattage then required but it has biiger heavier leads easier to wire and deal with. UNLIKE a Diode, the resistor provides at least some degree or current limiting.

HOWEVER if you insist on using a diode I used like a 5 to 10 amp rated unit, although again that's more then needed, but has bigger easier to manage and wire up leads.

If you use an idiot light it needs to be a small incandescent NOT an LED as they have too high resistance.

Or you can do as my friend Bob M and use an idiot light in parallel with a resistor so it still works even if the bulb burns out

Hope this helps, there are all your choices, so pick one and give it a try

John T

mmidlam · Apr 19, 2014

are you sure the bulb is getting 12 volts to one side? With key on and engine not running, ground #1 and light will glow if upstream circuit is ok. If light glows, alternator # 1 connection is loose or brushes are worn or springs weak.
If you get a no glow, then 12 volts is not getting to the bulb, there is too much resistance in the light feed...loose bulb in socket, bulb with too high of a voltage rating or too small of a current rating.

alternator charging again

INCase

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Janicholson

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JMOR

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Pappy

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John T

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mmidlam

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