JD 820 - 6 volt alternator on a 12 volt tractor?

jcalla · Oct 3, 2011

I had an old JD lawnmower that used a generator similar to the one shown. I rewired it myself. It was also the starter and after the tractor started would switch over to generating DC current. Worked great for 18 years until hydrostatic trans went, then I traded it in for my 455.

JPC

glenhenshaw · Oct 3, 2011

Does anybody know how fast the engine should spin at idle? If I knew that I could figure out how fast the alt is going (and the right size for the pulley).

And does it hurt anything to spin the alt below 400 RPM?

Soundguy · Oct 4, 2011

nope.. just won't charge...

soundguy

RickB · Oct 4, 2011

glenhenshaw said:
Does anybody know how fast the engine should spin at idle?

Off the cuff, no less than 800 ERPM.

jd110 · Oct 4, 2011

You might find that the alternator will work better after you get the new indicator bulb. With the broken bulb, the energizer circuit is open and it has to self-energize. That is the reason you need to rev engine to charge.