ET: Engine (Twin) Kubota Alternator

[Bill Cannon]

I'm getting no output from my Kubota rotating magnet alternator. I,ve checked for AC output directly from alternator and there is nothing.
I have checked the resistance of the windings and on my cheap multimeter is reads Zero. The windings are quite thick wires so this may be correct.
Anyone know if they should have a significant resistance.
Cheers Bill

 

[James B]

Bill

I don’t have a Kubota alternator but can say from general principles your output coil should measure a few ohms. If it’s really zero, you may have a short somewhere

Let me know if you need another pair of eyes on at some point - but I’m out of the country on hols at the moment

Best

James

 

[Pete Appleton]

I will measure one tonight if no-one else comes up with a figure in the mean time. Resistance from either wire to earth should be virtually open circuit. Any significant continuity will indicate burnt windings.

 

[Peter Holmes]

Bill, Is this a unit that has been working OK or is it newly fitted, I use a Nippon Denso that is fitted to a Kubota, but it needs a light bulb in the circuit to get it going, I think the technical term is excite, are you using the 16678-64012 alternator or the smaller pancake alternator where the exterior body rotates, as used with the Macdougalator, I have been using the former for a while, installed by Norman Walker and it has been faultless, they do have a built in regulater that can easily be changed, perhaps that could be your first port of call, my Son works with Kubota plant machinery, hence I had access to one, he tells me they are bullet proof, very rarely is there ever a need to replace them.

 

[Chris Launders]

I have an untried 2nd hand Kubota type alternator, rotating body external regulator type, reads 7 ohms across the two leads, generates 4v ac just spinning it over by hand.

 

[Bill Cannon]

Bill, Is this a unit that has been working OK or is it newly fitted, I use a Nippon Denso that is fitted to a Kubota, but it needs a light bulb in the circuit to get it going, I think the technical term is excite, are you using the 16678-64012 alternator or the smaller pancake alternator where the exterior body rotates, as used with the Macdougalator, I have been using the former for a while, installed by Norman Walker and it has been faultless, they do have a built in regulater that can easily be changed, perhaps that could be your first port of call, my Son works with Kubota plant machinery, hence I had access to one, he tells me they are bullet proof, very rarely is there ever a need to replace them.

Peter, this is the macdougalator type. It has had very little use but has been working. I am not using the standard V-belt drive so I took the half pulley off. In doing so I should have put a spacer in place of it and the magnet has been running skewed and has probably contacted the coil poles although there is no obvious damage.

 

[Pete Appleton]

I have two brand new alternators as used in the mcDougalator. Both show 0.3 Ohms between the two wires. As I mentioned above, resistance between either wire and the body is in the mega Ohms.

 

[Bill Cannon]

Thank you Pete, you have alerted me to the obvious thing I should have checked , isolation from earth and, sure enough, there is a short to earth. I'll examine further tomorrow to see if it is in the connecting wire or in the windings. If the windings then it's a trip down to our local rewinding expert.
Thanks again
Bill

 

[Bill Cannon]

I had the alternator rewound by someone I've used successfully before. I re-fitted it without checking the output (stupid boy Pike) and now find that it is still not charging the battery. Windings look fine and there is no short to earth this time. I have checked the AC output direct from the alternator and the most I get is about 10V at maybe 2500rpm, as fast as my drill will run it. I would expect a much higher unregulated output than this. Has anyone ever checked this?