1980 Porsche 924 alternator

  • 1980 PORSCHE 924
  • 4 CYL
  • RWD
  • 135,000 MILES
The alternator isn't putting out enough to any power to the battery. Even when use the throttle and give the car some gas, the voltage on the battery stays about 10-12 volts. Is there a fuse that could possibly be keeping the alternator from charging the battery or should I replace the alternator itself?
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have the same problem?
Monday, November 25th, 2013 AT 3:27 PM

1 Reply

First eliminate all other possibilities so you don't have the same problem after replacing it. Worn brushes and a failed voltage regulator will also cause the generator to not charge, but both of those are built into it. There's also an input circuit that could have a problem. Typically, when the voltage regulator is built in, that voltage comes through a warning light on the dash. If that light doesn't work, suspect a break in the wire going from the dash to the terminal on the generator. That circuit provides the turn-on signal for the regulator. If you have a gauge instead of a light, the same circuit is used but you won't be able to observe the operation. Check for a terminal on the generator that has less than 12 volts on it with the ignition switch on, engine off.

There also has to be a 12 volt feed wire to run the internal electromagnet. There's no reason they can't get that 12 volts from the fat output wire, but typically it comes in on a separate wire that's fused. That normally will have 12 volts all the time, but for sure it must be there with the ignition switch on.

Also be sure you have 12 volts on the output terminal. If you do not, you may also find you have real high voltage there with the engine running. That would point to a break in that wire where it goes back to the battery. There's usually a fuse link wire or a large fuse in that circuit.
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Monday, November 25th, 2013 AT 4:35 PM

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