Re: Alternators For Model As

Posted by Bob Carabbio on July 21, 1997 at 17:28:15

In Reply to: Alternators For Model As
posted by Bruce Wheeler on July 21, 1997 at 12:22:20

Sounds like your alternator is alternating, but your regulator isn't.

The voltage regulator does just that, and tries to keep the system voltage constant at about 7.2 or so for a 6 volt system, and about 14.4 for 12 volts.It sounds like your alternator is just putting out what it feels like without control.

With a discharged battery, it can take a while to get the battery back, and since the voltage of a discharged battery can get pretty low, the alternator puts out a heavy charge to get it back until the battery nears a charged condition and its voltage gets up where it belongs. It then ramps off to close to zero.

This shouldn't take more than 20 miles of driving though if the battery's any good.If it's still charging heavy after a long time, either the battery is defective, the regulator is defective, or the alternator has an internal short in the field circuit.

If you have a voltmeter, check the voltage at the starter terminal with the lights off and the engine turning over about 1000 RPM.At the beginning of this I gave the normal system voltages, see what's there.If the voltage is LOW and NOT rising slowly and the alternator is showing a heavy charge, then the battery is suspect (shorted cell).If the voltage is HIGH or normal, and the alternator is showing a heavy charge, then the regulator, or the alternator itself is defective.

You didn't say whether the alternator had an external regulator.If it does, disconnect the field wire (the lighter wire), and the alternator should stop charging immediately.if it does, then the regulator is probably bad or mis-wired.if it doesn't, then the alternator has a problem.

Make sure the regulator is grounded solidly, or it won't work properly.

If you're not using a small pully on the alternator, then at idle speed the alternator may not put out much since the "A" engine ticks over so slow.





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