Fri Feb 22, 2013 12:01 pm

what are the symptoms of a generator gone bad. thanks . Byron in CT.

Re: generator

Fri Feb 22, 2013 12:32 pm

It really depends on what is failing in the generator but some typical signs are noise from the bushings / bearings, noise from the commutator / brush area. Unsteady or reduced output voltage. I looked at a generator at DSCF that had only 1/4 volt output at high idle. If using an analog meter (my preference for generators) the needle may be very unsteady indicating problems with the brushes or commutator.
The other sign would be smoke! Once the smoke is released most electrical components quit working.... :shock:

Re: generator

Fri Feb 22, 2013 3:37 pm

What BigDog said plus, could be regulator or bad wiring (checking all grounding points) as well as generator problems if not charging.

Re: generator

Fri Feb 22, 2013 4:18 pm

Hi Byron,

For your question: "what are the symptoms of a generator gone bad", maybe try this.

1. Remove generator & with battery cables, touch the ground cable on the generator body while at the same time, touch the generator output connection with the other cable.

2. If the generator spins like a starter, it is good; if not it is bad.

3. If bad, either bring it to generator shop for test & rebuild; or, try to rebuild it yourself -- the first generator re-build takes longer; but the second one is a snap if you do not have too many senior moments.

4. If generator has bearings on both ends they are usually still good; however, if they have bushing, these bronze bushings can wear & should be replaced if worn because the armature can get off center & possible hit the sides & ground out.
Not a big deal to change generator bushings.

5. The more probable cause of generator failure is worn brushes & worn commutator. Worn brushes can cause the steel brush holders to move downwards & ground out on the commutator, and worn brushes can also cause the open grooves on the commutator to fill up with debris & ground out on each other in lieu of being insulated from one another.

6. Not a big deal to remove & provide new brushes. For cleaning comutator grooves, take a hacksaw blade & grind the sides on a grindig wheel so the teeth are narrow & clean out all commutator grooves to about 1/32" deep.

7. Prior to reassembly, get a test lamp or multimeter to insure continuity between each individual segment of the small diameter commutator to each individual segment of the larger diameter armature -- if no continuity, (sometimes rare), you need a new armature.

8. If you have any doubts about remembering re-assembly, use your cell phone to take picutes of disassembly so you can readssemble it to bring it to a repair shop & not be embarrassed to let the repairman know you could not fix it.

Hope this helps -- nothing like a good challenge !

Re: generator

Fri Feb 22, 2013 11:00 pm


Some nice to see you posting again. Hope you are well and still engaged in your design work.

Re: generator

Sat Feb 23, 2013 1:26 am

Hi Rudi,

Doing well -- still working -- thanks.

No doubt Byron is very intelligent -- like with many others, it is most admirable that he asks sincere questions on vintage equipment such as generators.

Maybe a "thought" for today when thinking about asking "Questions" on this Vintage Tractor Forum:

A. When a whole gang of non-hunters go elk hunting for the first time, it is easy to pick out the intelligent guys -- they are the ones who are brave & humble enough to first consult about the do's & don't details, & also the dangers involved with elk hunting with some old former elk hunter.

B. Also if one ever meets a top notch outstanding intelligent doctor that can quickly diagnose ailments during the first visit, he did not learn to diagnose patients by maintaining a zippered up mouth7 by not asking his former patients lots & lots questions.

C. Admit it or not, we all learned lots by questioning others. Vintage tractor mechanics are getting scarce.

Just trying to encourage Cub owners to continue to ask questions -- being a little informed makes much more sense than being a little un-informed.

Have a good weekend.

Re: generator

Sat Mar 02, 2013 11:10 pm

Ahoy "Cubbies".....suggest you not overlook the simple factors......I have found on my 1948 Cub that a loose generator belt....and it doesn't have to be very loose ...will prevent a good power output. You gotta spin it to gen it!

Re: generator

Sun Mar 17, 2013 10:51 am

Hello Rudi..... would you please refresh this [url]old[/url]Naval Aviation "sparky" the proper procedure for flashing the field on my 6 volt generator on my cub "Susie-Q". I saw a post on this subject several days past but, now I can't find it.

I like the way you present your expertise.

Chet sends

Re: generator

Sun Mar 17, 2013 12:04 pm

Chet, If by "flashing" you mean polarizing, here's a post from the CBoK: