both dynamo connectors the same, how to hook them up?

grossgary · Oct 3, 2008

i just installed a new dynamo on my B7100. both dynamo connectors are the same, so i don't know which way to install or how to determine.

is it possible it doesn't matter and it will charge based on how it's hooked up?

Tig · Oct 3, 2008

If it is truly a "dynamo" then it is polarized, so it does matter which way they are hooked up. Since you want the dynamo to charge the battery it should be connected positive dynamo lead to positive tractor lead. You will have to turn the tractor on and use a volt meter to identify these leads.
That being said I would like to see if others concur or have an easier method of identifying the leads.

grossgary · Oct 3, 2008

thanks steve. i'll fire it up and test them, as you know i got nothing with the tractor off.

thl · Oct 3, 2008

GrossGary,

The dynamo is an alternating current unit. So I do not believe that it matters what way the leads are connected. I had charging trouble on my B2150 and swapped them out to determine if that made a difference. I found later that it was a regulator plug issue.

Terry

Egon · Oct 3, 2008

Doggone Garry, here I had to get off my duff, hobble downstairs and go look at the tractor as it is sitting in the backyard.

I see two plug-in wires that have no color coding so I assume it matters not how its plugged in. Diagram does not distinguish between wire either.

Tig · Oct 3, 2008

If you do find AC voltage as Terry says then he is also correct about polarity not being important.
I thought dynamos were DC but I seem to be less than correct on that point.

LRH · Oct 3, 2008

These dynamos seem to be just like the simple stators on lots of older motorcycles; they just put out alternating current, and the rectifier and regulator or regulator/rectifier combo is located elsewhere. I have changed a few of the older dirtbikes from 6V to 12V by changing out only the regulator to a combo unit one for a lawn mower engine, and using gel cells from emergency exit lights. The M/C stators would put out 9-11V at idle and ~45-50V at 5K RPM's and ~90-100V (A/C) at WOT, with the reg/rect combo it would put out 13.4V DC at anything above 2.5-3K RPM's and allow a modern halogen headlamp to be used. Seems Kubota, and other manufacturers would not spend any more money to just build the tractors with an internal regulated alt assy, versus the dyno, a regulator/rectifier in a remote location, and a multi wire harness joining it all together.

grossgary · Oct 4, 2008

thl said:
GrossGary,

The dynamo is an alternating current unit. So I do not believe that it matters what way the leads are connected. I had charging trouble on my B2150 and swapped them out to determine if that made a difference. I found later that it was a regulator plug issue.

Terry

Bingo! Thanks Terry for spekaing up! Sure enough I got A/C current when I fired it up.

When I first started it, I got no measurement on the tractor/engine side leads. Not sure why they didn't show any charge, I would think they'd show something? But the dynamo showed 25 AC volts at low RPMS and 30+ at high RPMs.