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A Very Hot Generator
Posted: Sat Nov 29, 2025 8:30 am
by J1MGOLDEN
Yesterday, I went to help a friend do some repairs on his friend's newly purchased 1926 Touring T.
The engine started fairly easily, but I noticed the ammeter was not showing a charge with a fast idle.
The ammeter pegged when I did a jumper around the cutout to flash the field coils.
The generator terminal measured 26 DC Volts with my trusty Simpson 260 and the engine running at a fast idle.
The battery had measured 6.0 DC Volts across the terminals and I read the same voltage on the cutout to ammeter wire connection.
How that could happen is still a mystery!
Any suggestions?
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 8:51 am
by Dan Hatch
Sounds like the cutout has gone South and you may have let the factory smoke out of generator. If you haven’t let out it will soon get out on its own.
Better fix it before it gets out. Dan
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 10:06 am
by TXGOAT2
The cutout has evidently failed. DO NOT run the engine anymore until you ground the generator terminal to the generator frame with a short piece of wire. That will disable the generator and the engine can then be run without damaging the generator until another cutout can be obtained, but there will be no generator current available to charge the battery. The generator may be damaged, or it may not be. I would also disconnect the wire at the cutout that goes to the ammeter and tape it so it can't short out to anything. The cutout can be rebuilt or replaced with a solid state cutout, or better yet, replaced with a solid date regulator.
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 10:14 am
by Adam
If the cutout is a “Fun Projects” solid state cutout; when you jumpered it with a pair of pliers you fried it…
Also, if the battery read 6 volts there is something wrong with it or your meter. A 6 volt battery should read about 6.5 to 7.2 volts.
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 10:44 am
by Jerry VanOoteghem
J1MGOLDEN wrote: ↑Sat Nov 29, 2025 8:30 am
The ammeter pegged when I did a jumper around the cutout to flash the field coils.
The generator terminal measured 26 DC Volts with my trusty Simpson 260 and the engine running at a fast idle.
Did the ammeter peg towards the "charge" or the "discharge" side?
After you jumpered it, did the generator remain charging, or did the ammeter go back to zero?
By the look of it, he simply has a bad cutout. Running it with the ammeter at zero, and an open (bad) cutout, will quickly fry the generator.
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 11:26 am
by love2T's
TXGOAT2 wrote: ↑Sat Nov 29, 2025 10:06 am
The cutout has evidently failed. DO NOT run the engine anymore until you ground the generator terminal to the generator frame with a short piece of wire. That will disable the generator and the engine can then be run without damaging the generator until another cutout can be obtained, but there will be no generator current available to charge the battery. The generator may be damaged, or it may not be. I would also disconnect the wire at the cutout that goes to the ammeter and tape it so it can't short out to anything. The cutout can be rebuilt or replaced with a solid state cutout, or better yet, replaced with a solid date regulator.
Or even better yet...replace it with an alternator! The one "non-purist" thing I did that I'm glad for.
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 11:39 am
by TXGOAT2
Those new-fangled alternators emit Hertzian waves that cause falling iguanas!
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 5:40 pm
by J1MGOLDEN
The Cutout was bad from the beginning and the cause of my grief.
Ron Patterson called and explained the whole problem and outcome to me this morning.
I will replace the generator and CutOut, which I suspect is an early mechanical type, as this T was in storage for over 20 years.
I can also bench test the generator separately in my garage.
Thank you Ron!
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 6:35 pm
by speedytinc
J1MGOLDEN wrote: ↑Sat Nov 29, 2025 5:40 pm
The Cutout was bad from the beginning and the cause of my grief.
Ron Patterson called and explained the whole problem and outcome to me this morning.
I will replace the generator and CutOut, which I suspect is an early mechanical type, as this T was in storage for over 20 years.
I can also bench test the generator separately in my garage.
Thank you Ron!
Those cheap repop mechanical cutouts are generator killers.
You can spot them by feeling how light they are compared to original units.
Ford must have thought an ammeter important to install such a costly part. (the only gauge/instrument)
If you see your ammeter stop showing a charge, stop asap & ground the generator output terminal. If not, the gen spikes up the voltage & fries itself. Costly inattention.
Re: A Very Hot Generator
Posted: Sat Nov 29, 2025 11:32 pm
by Jeff
I make a 60A diode cutout or even better, put a voltage regulator on it and save your battery in the process. And never "flash" a generator with a VR installed or you will fry it instantly.
Beware of installing alternators on a T. The stock wiring is a fire hazard. I've written a very detailed article for Vintage Magazine on the pitfalls of throwing alternators in a T. If you do install one, expect to upgrade your wiring or you're literally playing with fire.
Jeff