Generator has no Voltage Output

[Married2Allis]

Testing 50 amp PTO generator yesterday. Eased the throttle up slowly to 540 rpm. The 'voltmeter' on generator (has no numbers -- just shows the sweet spot) started to come up into the correct range, then all of a sudden dropped slowly to nothing. Tractor PTO was running at 540, voltmeter showed nothing. Tried once more, same thing but worse -- never got close to the sweet spot then slowly dropped to nothing, stopped the tractor.

Then I noticed that I had left my voltmeter connected into one of the 120v recepticles on the generator. Did leaving the voltmeter connected fry it?? I looked in the parts diagram for the generator and noticed that it has 1 or 2 capacitors, a diode, and a varistor. What could have blown, a capacitor? The stator? - thanks.

 

[timcasbolt]

Try plugging an electric drill into the generator while it's running. Squeeze the trigger and rotate the chuck backwards. Sometimes exciting the generator in this way
can get them back to working again.

 

[Russ from MN]

If you put some non voltage sensitive load on it (light bulb or heater) and then bring it up to speed it might exite itself. Or use
the drill trick, I have done that.

 

[Married2Allis]

Russ and Tim, thanks for the answers. Had no idea. I'll try the drill trick. Suprised there is nothing in the owners manual about it loosing magnetism from non-use. Worked fine last year and sat until now.

 

[Married2Allis]

Tried to excite it with the drill. The drill started to turn in the other direction fine but not real fast maybe a few hundred rpm. Disconnected the drill, stopped the generator, then started the generator again and eased up on the rpms. Saw the needle on the gen voltmeter begin to rise, but fell right back down again. Must be something else going on. Has a warranty for parts only, essentially it's a new generator -- have to call the dealer tomorrow. Not looking forward to the 'authorized' repair experience. There is a very good old-fashioned electric motor repair shop nearby, probably talk to them first.

 

[guido]

Hello Married2Allis,

Sounds like the brushes and the commutetor need attention,

Guido.

 

[Married2Allis]

This is a brushless generator.

 

[buickanddeere]

Put a volt meter on the voltage regulator output

 

[boler76]

if it is brushless it probably has a bad diode in field that breaks down when the voltage
starts to rise ??

 

[jeffcat]

Trouble is this is a good trick but a brushless will not be excited. Others said Diode and another possible is a voltage regulator board too.

 

[Married2Allis]

Thanks jeff, called Northern Tool tech support this morning. Tech said that they start with the drill trick, then next thing is to try flashing with a 12 volt battery. Hopefully this will do it.

 

[buickanddeere]

It won't work . The drill or battery flashing is only for when there is no residual magnetism and no voltage generated .
Time to bite the bullet and start measuring diodes and VR output.

 

[Tequila]

Brushless generators most usually lose the capacitor. Take the leads off the capacitor and run up to 540 rpm. Check the voltage across the
leads. You should have between 4 and 11 volts. If you have voltage there, replace the cap. With a new capacitor with same values.

 

[buickanddeere]

(quoted from post at 12:15:36 12/14/15) Brushless generators most usually lose the capacitor. Take the leads off the capacitor and run up to 540 rpm. Check the voltage across the
leads. You should have between 4 and 11 volts. If you have voltage there, replace the cap. With a new capacitor with same values.

Use the multimeter to test the capacitor and the diodes. Why guess ?

 

[Charles in Aus.]

Had this happen twice now on different generators and once to a friend's , in each case the capacitor had failed . In one circumstance the case split and the capacitor's gizzards had fallen out , in the others they looked fine but had failed internally . The capacitor from a large electric motor will be a reasonable substitute , but then I only deal with 240 volts down here .

 

[buickanddeere]

. AC and DC capacitors are two different animals.

 

[Andy Martin]

You guys are slow too, eh, 50 cycle or so. I spent 6 weeks in Sydney on a job in the early 80's. Great place, great people, but the sun kept setting in the east. Kept me confused. Should have stayed.