How do I test for output from my generator?

Thanks Again
Bob F.

~Leave the voltmeter hooked up & short the [F] post on the generator to the generator case [is it showing above 7.2 volts now?] if so, your generator is probably working & your problem is more than likely a bad regulator, open in the field wire running from the generator [F] post to the regulator [F] terminal, or a bad regulator ground. [try a ground wire from the regulator case to the tractor frame]

~If it didn't show 7.2+ volts with the [F] post grounded, leave it grounded & run a jumper wire directly from the generator [A] post to the starter big battery terminal stud on the starter [the regulator is very hard to get to on the 420 so it is much easier to use the jumper wire to the starter post]. Does it show 7.2+ volts now? if so your problem is either an open in the wire running between the generator [A] post & the regulator [GEN] terminal, a bad regulator, an open in the wire running from the regulator [BAT] terminal to the [ammeter], or an open in the wire running from the [ammeter] to the battery cable stud on the starter. Use your volt meter & check for battery voltage at the [BAT] terminal of the voltage regulator, [if you don't have battery voltage there, find out why]

~If is still doesn't show a charge, leave the [F] post grounded on the generator, turn the tractor off & disconnect the jumper wire from between the [starter stud] & the generator [A] post. Then remove the generator drive belt & re-connect the jumper wire from the [starter stud] to the generator [A] post,, the generator should start to motor, now un-ground the [F] post & see if the generator picks up speed....If the generator doesn't motor at all, you have a generator problem like- dirty commutator, burnt out armature, stuck brushes, broken wire to the armature brush, bad generator ground, or other internal problem,,,if the generator motors but doesn't slow down with the [F] post grounded, you have field problems like- open in the field windings, broken field brush spring, stuck field brush, broken field wire, or other field related problem.

~Most people find that printing this test sequence out & taking out to the tractor will help keep things in order.

~If the tractor has been converted from 6 to 12 volts you could have the wrong generator or other change induced problems so post back if you have been converted to 12 volts...

You say you have a Voltage Regulator, so this answer is for a full fledged 3 or 4 wire true Voltage Regulator Circuit, and not a cut out relay or a light switch field control system!!!!! If thats what you have, post back for a diffeent answer.

NOW, to test if its a Voltage Regulator or Generator problem, with it running, use a jumper wire and connect the Field wire post out of the generator (smaller of the two posts) to ground and see if the ammeter (if it has one) shows better charge or the battery voltage rises. If it does charge better than without that jump, the generator is probably okay but you either have a faulty Voltage Regulator or a broken connection between the generators field post and the VR Field terminal, or a poorly grounded VR.

NEXT, if that jump doesnt make any difference, with it still in place and tractor running, try momentarily jumping together the Bat terminal on the VR to the Arm (Gen) on the VR and see if any ammeter shows more charge or the battery voltage rises. What that test does is check the Cut Out relay portion of the VR. NOW if neither of those jumps helps the charging, its likely a generator and not a VR problem, since those 2 jumps basically takes the VR out of the circuit.

Another way to test just the generator, is to remove its belt, and apply direct battery voltage to the Arm (bigger of the 2) terminals on the Generator to see if she motors and runs. If she does and if you ground out its Field terminal and she slows down some, the generator is usually okay.

Other things that can cause the battery to not remain charged are a weak cell in the battery or a short in the trator wiring. If everything is shut off and you disconnect and connect one of the battery terminals, there should be no small sparks, otherwise theres a trickle load short which runs down the battery. Have you had a load test performed on the battery???

Also, the battery can never be charged if theres not a good connection between the BAT terminal on the VR to the battery itself. That would be through an ammeter (if it has one) then to the battery, often via the starter post. A test lamp or voltmeter should indicate full battery voltage at the BAT terminal on the VR.

Let us know how these tests turn out and we can progress from there. Remember, this is for a Voltage Regulator type circuit as you indicated you had one. In the event you have a 3 brush generator, they can still use a VR circuit, and the closer the two brushes are set together, the more current that generator will put out. If it is a 3 brusher, move it to max charge and see if that cures the problem. Ol John T Nordhoff in Indiana