1949 Ferguson TO-20 Generator and Regulator Repair

I figured it was time I looked into the charging system on the tractor. It had a dead 6 volt battery in the compartment when I bought it so I was pretty certain the electrical system wasn't too far out of order. I pulled the generator and regulator off the tractor and took them to the bench. The generator didn't look too terribly bad in where the three brushes reside, but two of the three brush holders were stuck. A little oil freed them up. This first photo below shows the side with one brush. It's pretty clean in there.

This next photo shows the two other brushes. Most generators came with two brushes, but as I understand it, the presence of a third brush was to limit output current. A three brush generator has a two-coil regulator. A two-brush generator has a three-coil regulator and the third coil is what limits the current. Once I got the brushes in my generator free to move, I spun the generator up with a drill motor and I measured up to 15 volts on the Armature (A) terminal when I grounded the Field (F) terminal. Yay, the generator works.

These next two photos show the insides of my regulator. Yeah, it's rusty, like pretty much everything else I've taken apart on the tractor (except the generator, although its pulley-end bearing is very noisy and needs replacing).

I did take the time to clean up the regulator (after I'd ordered a new one on Amazon), just to see if I could get it to work. And you know what? It did work. In fact, it works too well. The output voltage is 8-1/2 to 9 volts, and it should be around 7.3 volts. I tried adjusting the voltage regulating coil but didn't get anywhere, so I'm glad I have a new regulator coming.

I had to solder new wires onto the dash's generator charge lamp socket to get it operational again, and I was very surprised the bulb still worked. The lamp comes on when the ignition key is turned on, then goes out when the tractor starts (well, more accurately, when the generator starts putting out voltage). Anyone familiar with older cars has seen these dash lamps.

This next image is the wiring diagram for the TO-20 tractor. This was invaluable for me to get everything wired up correctly.