Alternator not Charging

The link below gives some common interchange numbers. Click on the link, and read down a ways.

• MAD electrical

Some "self-exciting" alternators are made by simply installing a "self-exciting" regulator, and some self-exciting changeovers include some diodes, installed internally in the alternator.

By using the simple harness I have shown, a salvaged "junkyard alternator" can be used, as well as a stock replacement alternator for a Gm vehicle of the 80's era.

The "self-exciting" alternators in the size range shown here were never produced by GM.

They are aftermarket outfits.

Why not use a standard alternator, and this simple harness to connect it up? Probably cheaper, no special alternator or regulator needed, and it will charge from idle on up.

The diode is a 1N5008. The large output stud is connected to the ammeter or battery, just as you would with a "one-wire" alternator.

The red wire from the diode needs to be connected to a voltage source that shuts off with the engine, and you're done!

By it's "specs", it's WAY overkill for this job, but not expensive, and VERY durable.

On the "as-original" 3-wire units, the two flat regulator terminals connect separately to the 2 wires in the white plug in my photo.

Is your TO-35 a diesel? That would explain what you are doing with the battery disconnect switch.

You could do it that way, so long as the tractor is shut down before the battery disconnect is opened.

You could connect the diode lead to the big output stud, along with the other "voltage sense" wire that is already there, in my photo, as long as the battery is always disconnected.

On diesels, some folks connect the diode lead as you are suggesting, and add a two-terminal oil pressure switch that closes at about 4 PSI in the lead with the diode.

Then, when the engine is shut down, the oil pressure switch opens, and cuts the "excite" voltage to the alternator's #1 terminal, so no battery disconnect switch is required.