VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt 40 charging problem

My 1940 ammeter will suddenly go to de-charge intermittently. When I rev the engine (sometimes several times) it will begin to charge. I just replaced, for the 2nd time, the 6 volt voltage regulator. It worked great and then all of a sudden the ammeter showed a discharge to the left.

Could it be the generator brushes? Another faulty voltage regulator?

The original 6 volt generator was professionally rebuilt about 6 years ago. Only about 1200 miles driven since restoration. The vehicle has a new wiring harness. Generator belt is tight. Battery is excellent.

What tests should I perform to check charging system?

Thanks,
Curt

It sure sounds like something is intermittently grounding to cause that large current draw.

Actually, the ammeter shows not a drastic “peg” to the left, but rather a lack of charge indication to the right. It’s like the generator simply drops “off line”. In other words, the charging system seems to take a nap. I wake the charging system by revving the engine several times until it indicates a charge.

I’m wondering, what are the symptoms of worn generator brushes? Could generator brushes bounce out of position or get stuck too far away from the commutator (what ever it’s called). Defective voltage regulator?

I would replace the brushes and clean-up the commutator that the brushes ride on.

Thank you ChevNut.
I’ll certainly try that this weekend.

How best to clean the commutator?

Thanks,
Curt

Something non-oily like brake cleaner.

I also use about 600 grit wet and dry emery paper to remove any oxidation off the copper and scratch the grooves between segments as well.
Tony

Thanks Tony and ChevGene.

I think I’ll drive it around first and then when the ammeter does its jump to dis-charge, I’ll pull over and check to see if the generator is sending out current with my voltmeter.

After reading about the generator in the 40 service manual, it looks like I’ll have to take the generator out and disassemble it to replace the brushes, clean commutator? I’m sure I’ll need to, but just checking to see if there’s a better way.

Thanks again,
Curt

Technically you can replace the brushes with the generator still mounted to the engine. I would not recommend that approach especially if you have never done it before.

You do not need to disassemble the generator to replace the brushes. After you remove the strap at the rear end of the generator you can easily remove and replace the brushes through the access holes at the rear of the generator frame.

Replace one brush at a time to keep things simple. After you remove the first brush you can see the commutator and clean it.

Excellent news Rusty 37!!
Thanks,
Curt

Just a quick follow up.

I removed the generator, cleaned the commutator, replaced the brushes with a new set. Using the 1940 manual made the repair quick and easy.
Since the repair, the generator is working perfectly and I’ve been driving almost daily with no problems. Ammeter shows a good healthy charge with no intermittent discharge readings.

Curt

This is a follow up to the follow up.

My attempts to make the generator work failed.

I ended up sending my generator to the Filling Station for a rebuild. I am very satisfied of their contractors work. It looks like new inside and out.

I previously installed a “premium” voltage regulator (made in USA) from The Billings Company and got rid of the Chinese one. I also installed a ground strap from the engine ground bolt to the firewall. I removed the negative ground cable and polished to a high shine the contact/bolt area near the starter. I made sure all ground areas were clean and free of paint, grease, and dirt.

I installed the generator today. After a great test drive, I am hopeful I’ve resolved this headache. It’s never performed better. I hope it lasts!!

Curt