I did this trying to diagnose the alt on my 1990 Ford E350 motor home. I went through a 1-wire regulator before figuring out the stock setup, while retrofitting a (much better) third gen unit into a 2nd gen spot.
I had the thing on my garage floor, with jumper leads going to a car battery, and a drill with socket on the big ole nut inside the pulley.
What they don't tell you, but what makes sense, is the alternator will offer up more resistance when it's trying to charge the battery vs just sitting there. So it'll twist up on you. Had my boot on it so it wouldn't go anywhere and it still tried to torque away from me.
My voltmeter did show high 13's for voltage, and I was spinning the thing at probably less than idle speed. Remember the multiplication factor of a big crank pulley with small alternator one.
In my example, the regulator grounds a screw to excite the alternator, so I could just full-field the thing with +12v and a ground, simplifying things. If the VR is bad it's better diagnosed bolted to an idling engine, IMO.
I had the thing on my garage floor, with jumper leads going to a car battery, and a drill with socket on the big ole nut inside the pulley.
What they don't tell you, but what makes sense, is the alternator will offer up more resistance when it's trying to charge the battery vs just sitting there. So it'll twist up on you. Had my boot on it so it wouldn't go anywhere and it still tried to torque away from me.
My voltmeter did show high 13's for voltage, and I was spinning the thing at probably less than idle speed. Remember the multiplication factor of a big crank pulley with small alternator one.
In my example, the regulator grounds a screw to excite the alternator, so I could just full-field the thing with +12v and a ground, simplifying things. If the VR is bad it's better diagnosed bolted to an idling engine, IMO.