MTFCA Forum

On the way back from a car show yesterday, the generator on my 27 quit charging. Stock generator and diode type cut-out. Tested with a test lamp and no voktage at generator post when car is running. There is power coming to cut-out from battery. Generatotr had new 3rd brush insulators and new brushes about 2 years ago. What should I look for first?

Is the generator commutator shiny copper or a dark color? If dark use 300 grit on a medium length of wood and polish. Charging rate should come back .... If not available, try spraying the short shot of carburetor cleaner while generator is running.

Sometimes a pencil eraser can be used to clean the commutator. If the commutator has been turned, the insulators between the sections should have been undercut just enough to keep the brush touching the copper. If that was not done, you might get some arcing as it turns. The insulator in the brush plate could be broken. Lastly, one or more of the carbon brushes might be worn down so it loses contact with the copper. Any of the above could cause the problem.
Norm

Moxie26 wrote: ↑

Sun Jun 02, 2024 10:35 am

Is the generator commutator shiny copper or a dark color? If dark use 300 grit on a medium length of wood and polish. Charging rate should come back .... If not available, try spraying the short shot of carburetor cleaner while generator is running.

I REALLY don't recommend this. Here's why. The wire in both the armature and field coils are coated with an insulating lacquer. In some cases, 100 year old lacquer. ANY substance that dissolves lacquer should be nowhere near your generator. Carb cleaner dissolves this coating in milliseconds. The result is shorted windings = useless generator. New field coils and rewound armature is the only remedy after that.

It's best to figure out what wrong first. Zero voltage output could be one of many things. Shorted post, shorted fieldcoils/armature, shorted or open wires on brush holders. The cutout could also be shorted at the generator terminal. Remove it and test if there's output from the gen - a quick test won't harm your gen, but don't run the car like that.
Or, Take the generator out and inspect it. It only takes a few minutes to remove it.

Jeff

Thanks Jeff.. I appreciate being corrected . Oh, by the way, I did not do this to your generator rebuild you did for us, but was a a past past habit which is now dropped

Moxie26 wrote: ↑

Sun Jun 02, 2024 11:39 am

Thanks Jeff.. I appreciate being corrected . Oh, by the way, I did not do this to your generator rebuild you did for us, but was a a past past habit which is now dropped

No worries! Trust me, I've had the "you did what?" said to me many times since I've had my T... it's also why I can read forum posts and go down rabbit holes for days.

Thanks everyone for the info and suggestions. I will remove the generator at the first opportunity and post the results.

Tested generator today. No voltage coming out when car is running. Cleaned commutator, no difference. Took generator off the car, won't "motor" on 6v. Guess disassembly is nxt. Don't see any obvious problem with the brushes or their wiring after removing the band.Insulators for 3rd brush holder look good.

Just lift the third brush in its holder so it doesn't contact the commutator and then motor. Loosen the outer four screws that hold brush assembly so it can be moved to adjust and then retighten after adjustment.

By the way, to the cooment that it only takes a few minutes to remove the generator. If the car has a vaporiser rather than a carburetor (which mine does). there are few additional steps-disconnect fuel line and choke/mixture controls, remove float bowl/heating plate assembly. No big deal but if yo have a vaporizer, something to be aware of.

My cars have the vap. and I have no problem removing the generator without taking all that stuff loose. You just have to twist and turn it to get it out.

Thanks Jim. I'll try that next time. It just looked to me like it would be difficult so I removed the stuff to be sure.
Dave.

Check thin "hot plate" for holes after it gets cleaned, may need new replacement. Use high temp sealer on edges before installation . How's generator coming along ?

Hot plate is good. Replaced not too long ago. I had one fail on the road about 30 years ago. Luckily had one hanging on the garage wall at home which my Dad brought to me and we were good to go again. Taking the generator to a friend today to check the armature and field coils.

FundyTides wrote: ↑

Sun Jun 02, 2024 10:31 am

On the way back from a car show yesterday, the generator on my 27 quit charging. Stock generator and diode type cut-out. Tested with a test lamp and no voktage at generator post when car is running. There is power coming to cut-out from battery. Generatotr had new 3rd brush insulators and new brushes about 2 years ago. What should I look for first?

I wonder if it's a grounding issue? I had this a couple years ago with a generator and also and alternator before I ran a separate ground wire. That fixed it.

Any progress with your generator problem fix?