How do I test a GM 12v Generator/regulator for charging at the generator/regulator, not at the battery? Tested Gen/reg, and have good battery/wiring but stumped. Yes polarized. Just want to learn how to test. Yes I searched here and google and just looking for plain step by step instructions please. Thanks!
look for more than 12.5 volts on the wire that goes to the battery You can measure it at the regulator end of the wire, instead of the battery end of the wire. But it should be the same thing, mostly.
Spool up the RPM to 2000 or so and load up the generator by turning on headlights, heater blower, radio. Need to see a bit more than 14 volts at "standard" 77° F. temperature, and higher, as temperatures decrease from there. If you're testing charging there is no reason to measure anywhere but at the posts.
Start by testing the generator by itself. Take off the wires at generatot. On GM, Hook analog voltmeter to "Arm" or "batt" terminal on gen, then run it up to 1800 or so, and then momentarily ground the F terminal while you watch the needle, it should run wild, way over on volts, almost burying a needle. Don't do it any longer than to get that wild spike or to show just a couple of volts. If it does not run wild, it is not charging...same is true if shows one or two volts. digital VM suck on this test that needs to be done quickly, but might work. On Ford gen, you have to put 12v hot jumper to the F terminal, not a ground jump. Chrysler gen is grounded like GM for this test .
As stated a digital meter is not as easy to use as an analog. I keep a working 260 Simpson just for this reason. F&J is correct on how much voltage a 12 volt generator will put out when unregulated.
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