John Deere 4100 alternator trouble shooting

hammerit · Jul 26, 2020

Battery not charging, 12.7 volts at battery while running I think it should be 13.5 to 14.5 . There are only 2 small wires on the alternator I pulled the plug apart and checked voltage while running, have 24 volts AC so my problem is probably the voltage regulator? any thoughts.

beenthere · Jul 26, 2020

Can only offer this charging circuit diagnosis chart from the service tech manual for the 4100

Seems to come to the same conclusion you have. voltage regulator/rectifier....

Roadworthy · Jul 26, 2020

I concur that there's a good chance it's the rectifier or the regulator, but not knowing that one I'll also extend the possibility it's the brushes. If worn too far they can put out the proper voltage open circuit but it may drop significantly under load. If your alternator has brushes that's a good place to start.

hammerit · Jul 27, 2020

Thanks for your info . How did you access the service manual I have tried but no luck, would like pages 26,73,74.

beenthere · Jul 27, 2020

I bought the CD version that includes my 4300, but also includes the 4100.

Possibly, if you PM to member "joecdeere" and leave your email, he has been gracious sending out pdf copies if he has them. Worth a shot.

The pages come with a prefix like 3-26.. the 3 is a section identifier. Near as I can tell.

Where do you find your page numbers?

hammerit · Jul 28, 2020

I got the page numbers from the attachment on your first reply.

beenthere · Jul 28, 2020

hammerit
Gotcha.. see it now. Looked them up, as they are in the section 4
Attached each page, plus page 4-74 ran over to the next page with the Results. Hard to get them in correct order, but will try.