MTFCA Forum

I hade my generator rebuilt and it’s not charging correctly. My friend said they may have wired it for a positive ground. How do I check this?

What do you mean by not charging correctly? What is it doing, or not doing?

BTW, I have my doubts about your friend's theory.

John

it is all but impossible to solve a problem created in an anonymous shop, on a public forum with no other details

Be assured, though, that if this was a repair by a commercial shop, your results are not unusual and may in fact be the norm. For certain, your repairmen did not actually test their work and it's very unlikely they even set it up correctly.

It's just an unfortunate fact, and the reason why a properly remanufactured Model T generator costs around $400. Those will work, will have a warrantee, and will not leave the owner to search for clues on the internet.

If your shop will not give you satisfaction, they should give you a refund. In the absence of that, you will do yourself a favor and purchase the MTFCA Electrical Book from any reputable supplier and start going down a list of troubleshooting exercises found therein. Once you have done that, you may well find the book advises you as exactly how to proceed. If not, then after running the troubleshooting exercises, you will have more information with which to supply to the Forum for your search for answers.

Best of luck.

A Model T generator does not come with a voltage regulator unless an accessory voltage regular has been installed. A normal T generator charges about 5 amps when running at a fast idle or when driving at a speed around 25 or more MPH. It will show discharge with the lights on. If you do most of your driving with the lights on, you can adjust the generator to charge just enough to keep the ammeter at zero with the lights on. That would be about 10 or a little more amps with the lights off. That will overcharge the battery unless you turn on the lights frequently even during daylight hours.
To adjust the charge, take off the band at the rear of the generator and on the top of the commutator, you will find a brush which can be adjusted by loosening the small nut and sliding the brush toward the engine which will increase the charge and away from the engine to decrease the charge. Be careful not to crack the insulation to which the small bolt is connected or the brush won't stay in place. When it is set the way you want it, tighten the nut. If it does not charge at all, you have other problems with the generator. The club publishes a booklet called "Electrical System" which contains instructions for a do it yourself mechanic. It will give you more details than I have in this post.
Norm

John L wrote: ↑

Mon Nov 28, 2022 7:53 pm

My friend said they may have wired it for a positive ground.

That would take a lot of work. If it's outputting a reverse polarity current, it's more than likely been flashed with reverse polarity (if someone has assumed a Model T was postive earth). In which case, flashing it with correct polarity will fix that.
Aside from that, "not charging correctly" does not give any information to make a diagnosis from. What is it doing incorrectly?

Possibily the ammeter is wired in reverse. Especially the 26=27 T's The ammeter looks just like a Model A ammeter and is interchangeable, however, the A has a positive ground so if you use an A ammeter on a T you must reverse the wires. You can tell if you turn on the lights and it reads charge instead of discharge.
Norm