generator

A generator is a tough piece of machinery. It doesn't break often. The voltage regulator box which includes the cutout relay is fragile and far more often the culprit when the generator doesn't charge right.

If a generator has a problem its most often worn out brushes and then bearings, then the pulley.

There isn't much YOU can do inside the voltage regulator box to make it better. If you dig in, you will probably make it worse.

You might be time and money ahead to take tractor with all the parts on it to an automotive electric shop and ask them to fix it. The local one does that often, though most often they are putting new diodes and bearings in alternators, new brushes, bendix and bearings in starters, and stuff like that.

Otherwise you can shotgun the problem and go buy a new regulator and a rebuilt generator from a car or tractor parts place and hope the problem isn't really a bad crimp lug on a wire.

If it was me (and I had practically that problem three years ago on my JD 4020 with generator) I added a permanent ammeter to the dash (there were spare openings not cut all the way through for the gauges used with a power shift transmission). Then I found the voltage regulator (after I'd cleaned the commutator, put in new brushes and put on a new belt and generator pulley) was sluggish to the point of bouncing the ammeter off the pegs at both ends of the scale. I knew the generator was underrated and that I was having to charge the battery far too often, so instead of spending $43 for a new voltage regulator, I went to the local auto electric shop and they assembled a one wire Delco 10-SI alternator with a small pulley that fit the JD belt width and a bracket so it fit the generator bracket. With that installed I see the charging happening as I've described and I've not had to charge the battery since. Not even after sitting over the winter or for starting with snow on the ground. Its what that charging system needed. I have a collection of JD service bulletins and they offered a kit for that the year after my tractor was made and supplied alternators with tractors having air conditioned cabs. Its not original, but it works far better than the inadequate original 20 amp generator.

I didn't go to the alternator until I proved the regulator was bad. Its not the best diagnostic to say the generator isn't charging and to discard it for an alternator.

Gerald J.

The generator can be perfect but if the regulator is out of adjustment, has rusty parts or burnt contact points, or is just missing the case ground, the pair won't charge. The best test is an ammeter in the battery charge and load line. Everything but the starter should pass through the ammeter. Then the generator shows charge or discharge on the ammeter and proves the quality of the battery, the generator, AND the regulator.

Working more slowly you can check the specific gravity of the battery electrolyte over an hour of running (well above idle speed) to see it if rises. If the battery is pretty good you can also check the battery terminal voltage with a digital volt meter to see if the voltage rises. It should get up to 7.1 volts for a perfect 6 volt system, 14.2 volts for a perfect 12 volt system.

If the voltage setting on the regulator is perfect, the ammeter should show maximum charge right after starting, and should taper down to zero charging current in time. A double check of full charge is finding the gravity of the electrolyte is 1260 in most common batteries. And seeing that there is a bit of bubbling of the electrolyte as the battery charging current has gone to practically zero.

Old generators tend to need the commutator cleaned, the brushes replaced or at least sanded to fit the commutator, an often they need bearings and pulley. When the pulley sides aren't V shaped any more the generator may create almost enough voltage to charge but won't supply the current to charge in any reasonable time. A glazed generator belt does the same. It will show voltage to a voltmeter but not put any energy into the battery. A glazed belt cost me a car once.

Gerald J.

Unless you have a magneto, where would you get the energy to feed the ignition coil? Battery or other voltage source which is the gen.

Sounds like correct diagnosis to me.

Mark