Bench Testing Alternator

[Red Diamond]

I can spin the alternator with a drill motor and a drill bit that is larger than the milling boss of the alternator shaft. I'm not that familiar with the connections I need to make with the Volt/Ohm meter to get a reading of the output. Any info would be appreciated, also the settings for the meter dial knob is needed. TIA

[Thunderbolt]

 I'll take a guess at it.  You will need to set the Voltmeter to DC Volts at the scale that is above 15 Volts.  If the meter is autoranging just set it to DC Volts.  Put the red lead connected on the meter to Volts/ohms and to the large wire connection point on the Alternator.  The black lead would connect to the case of the alternator.  Did you check it before you removed it from the bike?  Have you rebuilt it and just want to check it before re-installing?  I don't know how fast you would need to spin it or how it is geared inside the bike.  Let us know how it comes out.

[Gryphon Rider]

First of all, i think it's a bad idea for an electrical novice to "bench test" an alternator by spinning it. You really need to know what the heck you are doing. It's not just a matter of spinning it and measuring voltage at the terminals. For the alternator to work properly, it must be connected to the battery.  The terminals where the heavy white wire and the lighter gauge black & green wire connected must both be connected to the positive battery terminal, preferably with wires of equal or heavier gauge than the ones disconnected. Also, the alternator must be grounded to the battery negative. I can't remember if there is a ground wire or the mechanical connection of the alternator housing to the engine provides this.  I have no idea if its possible to have the alternator connected to the bike's wires and still be able to drive it with a drill, but I think that would be preferable to trying to rig up connections on a bench.  The best way to test the alternator is with it installed in a bike that runs. Would you mind telling us why you need to test it off the bike?

[Skinhead]

I believe the field windings of the alternator need to be powered in order to create the magnetic field necessary to generate current.  Otherwise, just spinning the rotor will result in nothing more than rotational motion and no output.

As others have stated, check the output on a running bike, or take the alternator to a shop/autoparts store that can bench test it.

[bentwrench]

Try a local starter/alt shop.They might be able to adapt their tester to spin it.bench testing w/out a proper load is meaningless anyway.

[Red Diamond]

Thanks for all the information gentlemen, you're telling me all I need to know, (Leave it to the professionals).
I have several alternators and have forgotten which is bad because I didn't mark them, which is why I thought of bench testing. Thanks again.

[gordonv]

If you are unsure, what about taking each one apart, clean, and inspect for repair?

Brushes, connectors, what ever you can buy the parts/repair kit for. Unless a winding has gone, which should be testable via info in the service manual, it should be able to repair with a basic knowledge and mechanical skills.

Then you'll have a few spares for yourself, and some other local riders.