Generator overcharging

Jembow

Jembow

Senior Member
Had the generator rebuilt, it now puts out 20+ amps and moving the 3rd brush makes no difference. Rebuilder says it doesn't matter as long as voltmeter shows about 7 volts going to the battery. I think he's wrong. Is the 3rd brush perhaps not wired into the windings? So the generator thinks it's a 2 brush unit.
 
20 amps will soon boil your battery dry ! Headlights on does that make the amps go down ? Battery connections clean bright and tight ?! Especially the ground connection to the chassis ! Also maybe your battery is almost dead ! Check it with a load tester .
 
Some folks would run higher amps so they could drive at night a lot. If a person does that then they should use the lights all the time. I like it to read 5 or 6-amps with lights off at road speed but I still run an original amp meter. The reproduction ones aren't as reliable.

It sounds like your rebuild needs a diagnostic or the amp meter should be checked against a calibrated unit. Depending on the type of generator, it should be able to adjust down at least to 4-amps or less with the engine running at idle. The output really shouldn't go above 10-amps and that would only be for night driving.

Shifting the third brush away from direction of rotation or toward the ground brush will increase amperage. Shifting in the direction of rotation or toward the power brush will decrease the amperage. The change should be checked with a sensitive meter known to be accurate. Ford mechanics had a test set up back in the day and a person could check the accuracy of the dash mounted amp meter with it.

In operation, the ignition coil should draw 3 or a little more amps. The brake light will draw a little at a stop. Head lights can draw a lot depending on the bulbs being used. Some folks are going to LED types to keep the current lower. It's not unusual for the amp meter to drop into discharge when lights are on. With nothing on but the coil, there should always be a charge even with the brake lights on at idle.

The model A electrical system was designed for a single tail light so it would charge most of the time but folks quickly went to 32cp headlamp bulbs and some even higher plus some add a second tail light. All this stuff and even the panel light taxes the original system. Turn on the electric wiper if equipped and the head lights and the system generally isn't going to keep up very long. A good battery will carry it but not for a very long time.
 
You should ask the shop that did the work to explain why the third brush is not regulating the amp output.
 
The rebuild guy clearly doesn't understand 3 brush systems. I'm going to start with going through all the connections to make sure they're clean. The only electrical items are headlamps and a single tail lamp. That only drops it to about 10 amps at driving speed. The battery is fairly new but it also happened with a different battery. I will report back when I get to it.
 
I suggest adding the voltage regulator that fits inside the generator. Your battery will thank you. One other thing to check is for loose or corroded electrical connections to the battery or to the grounding point on the frame. Also check to see that the generator is grounded.
 
If its charging at 20+ amps and moving the 3rd brush does nothing, the field wire is either attached to the output brush or the field wire is somehow touching the output wire or terminal post. Field strength determines output current. The stronger the field magnetism the higher the output. Normally the 3rd brush position determines how much current flows through the fields and the field strength. At 20 amps somehow max current is going through the fields. Your rebuilder did something wrong.
 
Rebuilt like you would rebuild a generator aimed at a Voltage Regulator system?


These include an extra wire which is the "supply" going to the field winding. The VR works to "flash" the field intermittently and keep the output voltage of the generator at 7ish.


Meanwhile on a Model A unregulated generator, you shift the "pickup" relative to the field and thereby control the generator voltage.


Thousand words...


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Conversely, the later "regulated" generators are set up around the following connections: (AI Overview: "Regulated Generator Wiring")

"Field Wire" (F)
"Armature Wire" (A or D or "Gen")
"Battery Wire" (BATT typically)


He may be "assigning" these values in his mind. "Oh this one goes to the field."


Joe K
 
I went through all terminals. Everything is clean and shiny., no change
So I swapped to a powerhouse generator I have, 10 to 12 amps at cruising speed, 6 amps with headlights. I believe in running with headlights so I think this will do. I may strip the other generator myself, the guy in the shop is adamant that 20 amps is fine. Thanks for all the help.
 
Jembow said:
I may strip the other generator myself, the guy in the shop is adamant that 20 amps is fine. Thanks for all the help.
Click to expand...

I suggest you avoid that shop. He clearly does not understand 90+ year old 3-brush charging systems and is too arrogant to admit it.

I'd be glad to help you out offline. Email me at splitdorf@cox.net.
 

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Steve can also set you up with a voltage regulator to stop the battery overcharging (high amp output). He has them for the long-style and powerhouse generators. You can also contact me at hill.mf@gmail.com
 
Instead of throwing out email addresses on a public forum and attracting anything unwanted, why not use the secure messaging this site offers?
 
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