VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 Generator

The generator in my 30 standard coupe pegs the gauge at + any rpm over 1000 and returns to a little over plus at idle. Time to rebuild ?

It's at least time for some repair work if not a rebuild.

First: Don't continue to run it that way -- it will very quickly overheat and burn the windings if it hasn't already done so.

Assuming that the ammeter doesn't go to full discharge when you turn the ignition switch on (indicating a short somewhere in the electrical system), the generator itself is very likely the problem.

If you're used to doing electrical work, you can do some preliminary checks yourself. If not, you may want to remove the generator and have it rebuilt by someone who knows these old units well.

Assuming that it's an original generator using output control with a third brush, you should first remove the inspection band around the brushes and have a look. One possibility is that the brush rigging has failed and is shorting out or one of the brushes has broken off. Another is that the wiring has shorted to the case or is damaged. Look also for signs of overheating.

Another (remote) possibility is that the output adjustment (third brush position) has slipped. It is clamped in place by the fillister head screw in the end plate -- you could check that the screw is still tight. Instructions on how to set the generator output by moving the third brush are in the repair manual --- be aware that if the third brush is BADLY out of position, the output can go uncontrollably high (or to zero).

If nothing is obviously amiss on the brush rigging, brushes, third brush position or commutator, you should remove the generator and either tear it down for testing yourself or have it rebuilt.

Good luck with it. I'm sure others here on the forum will have some thoughts as well.

All the Best, Chip

Your generator should be a Delco 943J so look at the Delco-Remy tag on the generator and see if you have the correct generator. If you don't have the correct generator, then I suggest that you don't waste money on rebuilding your current generator. Instead you should find the correct generator and then rebuild that unit.

The machine screw on the end-frame of the generator that holds the third brush in position should be a 10-32x5/8" round head slotted screw. To adjust the generator output, loosen that screw and move the third brush towards the engine. That will decrease the output of the generator. At speed, with the lights off, your generator output should be around 8 to 10 amps.

By the way, the third brush, which is the output brush, is the brush that is on top of the generator.

Adjust the third brush. If you don't know how, send me your email address and I'll send you instructions. It's easy.

Peter Z.

Or check out Peter's diagram here.

http://1931chevrolet.com/specs11.htm

--Bill B

Thanks Bill. I forgot this was on line.