The Stovebolt Site Forums The Shop Area The Electrical Bay How to test a generator

Hi All,
I did a search but did not find the answer. On my "new to me" 235 the generator does not seem to charge, nothing indicated on my gauge. Is there a way of testing the output of the gerator directly on the two wires coming out of it? Is there a way of knowing if it is a 6v or 12v generator by just looking at it?

Thanks,
skipper

Black tag = 6v, Red tag = 12v. Put a meter across the battery and see if the voltage increases as you increase the engine speed. It it’s not mounted on the engine, then take it to an auto parts store, most have a dynamic set up for testing generators and alternators.
Denny Graham
Sandwich, IL

A generator needs "residual magnetism" to be able to develop a voltage. If it's mounted on the engine with the wiring connected, make a momentary connection with a jumper wire between the regulator wires, "Bat" to "Arm". There should be a pretty noticeable arc when you connect, so only leave it connected for a moment. Once it's polarized, the "arm" terminal on the generator should produce about 1/2 volt or so with the generator turning and all the wires disconnected. Once you find that the generator can produce residual voltage, reconnect the wires and attach a jumper wire from the "F" terminal to ground. The voltage at the armature terminal should rise without limit as the engine speed is increased. Don't go much above a fast idle, as high voltage output can damage electrical accessories.

If the generator can produce voltage by grounding the field terminal and it still doesn't charge the battery, the voltage regulator or cutout relay in the regulator assembly could have problems.
Jerry

P.S.: Check out the article I put in the tech tips for some quick and dirty basic training on DC generators!
Jerry

Thanks all,
I will give it a try this week, I hope. There does not seem to be any tags on the generator red or black. I am assuming it is a 12v generator.