Need some help with '3rd brush' generator.

jjbubaboy

Hey all,

So I basically understand the 3rd brush generator and how it operates. What I dont get is how to adjust or regulate its output. I dont see any way to adjust anything and just recently my amp idiot light glowed on. Whats the correct fix?

Thanks again,

T Jeff

barrysweet52

Just loosen the screws or bolts on the end of the genny & rotate the inner adjustment, then retighten the bolts. Do so with a multi meter to get the desired volt/amps. I bought a 37T with an older battery. The last owner had it adjusted pumping out max amps. This is good if you do a lot of starting or night driving. Ive heard of people going on long trips during the day with the headlights on so that the battery doesnt overcharge. Im thinking they must have easy to change headlight globes, or more readily available cheap headlight lenses.



I went on a 2000km drive to a national rally in Aust and replaced a 20A fuse in the charging system about 10 times. It blew once coming down a steep hill and I thought the muffler must have been blown off with the load bang. Not happy with various diagnosis from a few people I called in to an auto elect on the way home. The genny had been adjusted to give over 7volts & 30+amps. No wonder the fuse kept blowing, and the battery water needed topping. The points looked like they had been hit with an oxy torch. Good luck, Barry

Park_W

I recently took a different approach for my '47 ... swapped out the gen and VR with ones removed from my Hornet when I converted it to 12v. The '48 and later equipment gets rid of the "somewhat regulated" third brush system and gives you a truly regulated output voltage at 7.2 or thereabouts. Eliminates the overcharging on long trips, etc.. The generators look almost identical but the regulator is a bit longer. Not too much of a hit on original appearance. The later regulators don't have the "T" terminal for the idiot light, so you just connect that wire to the ARM terminal of the regulator. Works fine.

jjbubaboy

barrysweet52 wrote:

Just loosen the screws or bolts on the end of the genny & rotate the inner adjustment, then retighten the bolts. Do so with a multi meter to get the desired volt/amps. I bought a 37T with an older battery. The last owner had it adjusted pumping out max amps. This is good if you do a lot of starting or night driving. Ive heard of people going on long trips during the day with the headlights on so that the battery doesnt overcharge. Im thinking they must have easy to change headlight globes, or more readily available cheap headlight lenses.



I went on a 2000km drive to a national rally in Aust and replaced a 20A fuse in the charging system about 10 times. It blew once coming down a steep hill and I thought the muffler must have been blown off with the load bang. Not happy with various diagnosis from a few people I called in to an auto elect on the way home. The genny had been adjusted to give over 7volts & 30+amps. No wonder the fuse kept blowing, and the battery water needed topping. The points looked like they had been hit with an oxy torch. Good luck, Barry

Hey Barry,

That sounds good but I dont see any way to rotate anything. The bolts go through the end plate and the brush assemblies seem to be fixed to the end plate. The end plate is notched to fit a certain way on the housing as well.

Guess I dont get this as well as I thought!:p

Still needing help.....

T Jeff

Geoff

I'm sure you will find the third brush, (that's the one you can see through the opening) is on a slide fit mounnt which will move around the commutator with a bit of leverage. Move in the direction of rotation to increase the charge rate. But I would agree with Park, change over to a two-brush unit and regulator, and you can forget about altering the charge rate, it will be automatic and far morbattery-friendly.

Geoff.

jjbubaboy

AHA!!

Thanks Geoff!

I took it out and opened it up and now I get it! WOO HOO

The plate with the brushes does rotate -OK.

Now my question is-I have a volt meter so do I hook it to the post that goes to the brush or the field?

What should I set it to for the amps to be OK? And are they relative or should I get an amp meter?

By the way its an Autolite GAR 4702 unit.

Thanks again!!

T Jeff

mars55

Yes, you are going to need an ammeter. Disconnect the wire from the "B" terminal on the regulator and connect the positive ammeter lead to it. Connect the negative ammeter lead to the "B" terminal on the regulator. Connect the positive voltmeter lead to ground and the negative voltmeter lead to the "B" terminal on the regulator. Ground the "F" terminal on the generator. Run the engine at approximatey 35 mph speed. With voltmeter reading 8 volts adjust the 3rd brush to get the maximum amps for your generator which is 15 - 17 amps. However, I think you have problem with your changing system. Try connecting the voltmeter to the "A" terminal on the generator and ground the "F" terminal on the generator. You should get about 8 -9 volts or more voltage then it was before you grounded the "F" terminal. If the volage does not increase, you have a bad generator.

jjbubaboy

Thanks Mars!

I will give it a try.



Jeff