Re: Hitachi alternator

Wed Oct 09, 2013 3:04 pm

My only thought on the wiring diagram besides the lamp/resistor mentioned by ArtC was the 30 amp fuse on the amp meter to bat terminal on the alternator and the 10 amp fuse on the headlight switch to B terminal on the alternator.

Alternator out put above 30 amps will take out both fuses.

Re: Hitachi alternator

Wed Oct 09, 2013 7:01 pm

The 30 amp fuse protects in both directions, if the alternator fails, the fuse will blow and protect the battery and wiring. If the alternator is charging the battery more than 30 amps something is wrong and it'll prevent burning up the wiring harness. The 10 A fuse is standard on a SA and if for the lighting circuit only, the alternator does not charge thru this path. Standard SA lighting will not blow the 10A fuse unless there is a fault.
I added the 10 ohm resister in series with the diode for two reasons. At start, it reduces the current going into the L terminal from about 2 amps to .75 amp, reducing the current required by the battery at starting is important if the battery does not have a good charge after sitting a long time. And it protects the diode from faults like accidentally shorting the L terminal when installing or testing. Not absolutely necessary but a good practice. This way the diode will survive an accidental momentary short to ground.
Gerry

Re: Hitachi alternator

Fri Oct 11, 2013 5:39 pm

RustyKnuckles wrote:Hmmmm...... Not sure I understand why the starter keeps turning the right way, but...

Anyway -
What happens if you run the 6v starter on 12v? Obviously shorter lifespan? Smoke and fire?


Hi all, new guy here. (have a 49 Cub)

If I may... the starter has no actual magnets, only two sets of electric coils that work together. Outer field coils on the casing, and inner coils on the armature. The same voltage is applied to both sets, so both magnetic fields always match up correctly. So no matter what polarity is hooked up, always turns the same. If you reverse only one coil set, that's different.

Guy on ebay sells the 12v field coils as a kit if you really like to replace stuff, but the starters seem to generally hold up okay.

Gary M