Battery Connectors

Check the ignition coil polarity connection. If positive ground the + terminal on the coil goes to the distributor points. If negative ground the - terminal on the coil goes to the points. Then check the ammeter connections. For negative ground the - terminal goes to the battery and the + terminal goes to the generator. For positive ground the + terminal goes to the battery and the - terminal goes to the generator.

For one more check, hand crank it without the battery and check the polarity of the generator voltage if you can get it to run.

The fits of the cables to the battery posts are a hint of the polarity the different sizes of the posts is there to help you get the battery polarity to match the system polarity.

If the ignition is magneto, its independent of the battery polarity.

Gerald J.

Hook it up the way the cables will allow. The starter doesn't care. The lights don't care. If the generator charges the battery you're good to go. Someone may have reversed the polarity once upon a time. As long as the ammeter is pointing correctly and the battery is charging, it doesn't matter.

If the generator polarity is opposite of the battery polarity, both the generator and the battery can be destroyed.

A simple ammeter test is to turn on the lights with the battery connected but the engine not running. The ammeter then should show discharge providing the lights aren't controlled by the generator voltage regulator. In that case borrow a headlight and connect it to the battery terminal on the voltage regulator and the ammeter should show discharge if the battery charger matches the ammeter polarity.

The destruction of the generator and battery is prevented by following the op manual instructions for flashing the generator, basically jumping the battery to armature connections on the voltage regulator to magnetize the field poles to give to generator polarity the same as the generator. Otherwise the generator and battery with opposite voltages are completely shorted and that is hard on them and the wiring between them including the voltage regulator cutout section.

Gerald J.

Hook the battery up the way the cables fit. Then, before starting it, temporarily flash battery voltage to the field terminal on the generator a couple times. Then you are good to go with no problems. You could also just disconnect the generator before cranking it over or running it and have no problem.

Don't flash the field terminal flash the armature terminal.

I have found some manuals at:
http://grandpas-tractor-site.s3.amazonaws.com/manuals/ac

The shop manual that I have at:
http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf
has the wiring diagram. I'm sure it was shipped positive ground.

Gerald J.

After replacing the battery, especially after it sitting without a battery or with a completely dead battery if it did, you should flash the generator anyway to be safe.