Generators - 12v 30 amp, new, no core

Generators supply the battery with voltage. To test a 12v generator, take the wires off the D+ and the DF terminals. Grab a volt meter and hook up the volt meter so the positive lead goes to the D+ and the negative to the DF. Now run a jumper wire from the DF to the D-. Start the car and rev the motor. If the meter pegs, the generator is good and if it doesn't, then it's bad. Now if the meter jumps to lower voltage the generator may need to be polorized. To polorize a generator, make sure the voltage regulator wires are still disconnected. Take off the generator belt. Using a battery with jumper cables, hook up the positive to the D+ and the negative to D-. Now with a jumper wire, go from the DF to the body of the generator. Hold the wire there just long enough to see the generator spin like a motor; no longer, or you will burn up the generator. Some generators are sold on exchange.