1969 JD 4020 Alternator

[kurt.reynolds]

First off, this tractor is something of a hobby for me, not necessary to maintain our farm.

I just finished converting to a single 12v battery vs 2 6v's, It was starting really hard and after going to a single battery, turns over as good as my car, and starts much easier.

I measured the battery voltage before starting and after running and the battery is not charging. Based on my experience with cars, this is an indicator that the alternator is bad.

Is there something else I might or should check before I replace the alternator? It cost $123 for a replacement, so not a huge expense. The alternator that is on there is a remanufactured alternator TY1430, according to John Deere site it has been replaced with a Starter SE501357.

Anyway, pulling the alternator today and will check the wiring and such when I take it off.

Picture of new fenders to make post more interesting.

 

[J.Wondergem]

Have the alternator checked. They don't usually charge for that.

 

[fdt860]

Your alternator will not work if the wiring is uncorrect OR the generator light on the dash does not work with ignition on and starter shut.

 

[susandiane]

The quick and dirty check of an alternator is whether the steel cap on the rear covering the shaft is magnetic when it's running. If it's not magnetic when running it's not working at all. It's possible for it to be
working but putting out only about 12 volts, not the 13 1/2 to 14 it should be. If the back of the alternator is inaccessible you can also see of the spinning shaft/pulley is magnetic. A flat blade screwdriver that's
NOT magnetic can be used either way, but very carefully if checking the spinning pulley/shaft!!