The Stovebolt Site Forums The Shop Area The Electrical Bay 63 Chevy Alternator

Interested in any information that would help me to understand when to replace an alternator on my 63 Chevy pickup and how to determine what type to replace it with. What would indicate it is faulty or going bad? And could I upgrade it to something more powerful or efficient? Thanks.

One way I use to tell if an alternator is going bad is to get the engine running and take a screwdriver and put it near the center of the rear of the alternator. If there is significant magnetic pull, it's usually good. But keep in mind, it's shade tree mechanics and not 100% accurate. One sure fire way to tell is take it to an auto parts store and have them bench test it. You can always upgrade but if you don't have a lot of accessories needing extra power, why spend the extra money?

OK, thank you. Very helpful. I'll try that first with the screwdriver. I don't have any extra accessories really, just the regular lights. Have a post about a starter problem I'm having so I was wondering if the alternator could have anything to do with it. I also want to put a more permanent power inverter in, but the things I want to run on it shouldn't affect it too much because I am able to do that now with my cigarette lighter just fine.

Put a volt meter across the battery. It should show about 14 volts with the engine running.

Find a dark spot at night. Turn the headlights on and the heater fan. With the engine running, watch ahead as you speed up the engine. Then let the engine idle as you turn the fan off, then shut the engine off. All this time observing the brightness of the headlights.

All this with the truck sitting still and you in the drivers seat of course. This is a quick, easy and safe way to give you a good idea. Of course the best thing would be a working factory ammeter.

If it's keeping the battery charged, there's no reason to replace it. With the engine running at fast idle (1500-2000 RPM) you should be able to measure 14 volts or so at the battery posts with a digital voltmeter. Depending on the state of charge of the battery, that voltage could vary from 13.5-14.5 with no problems. Beware of a voltage below 13, it usually means the alternator is not doing its job right.

Next test- - - -also at fast idle, turn on every accessory you can- - - -high beam headlights, high speed heater blower, high speed wipers, cigarette lighter, etc. to put as much load as possible on the alternator. Check the voltage at the battery again. It should be 13 volts or more. This checks the alternator's ability to keep up with the current demand of the accessories. If the charging systems passes these tests, don't mess with it. People who recommend a super high-output alternator like a 100 amp or more have no understanding of what a charging system is supposed to do. The only reason for going to such a ridiculous amp output would be to support a mega-watt sound system, or a set of hydraulic pumps for a lowrider, or something equally stupid!
Jerry

OK, thanks for all the help with this. I really appreciate it.

The alternator you have is most likely an external regulated one. So if that is the case...if. Then you will have a regulator on the fire wall. You need to get a voltmeter(about 5 bucks on sale at HF) follow the tips in the shop manual. Works a lot like the regulator on a generator system. The above suggestions are good ones.