Generator

At 500 engine RPM a good generator should start to put out a hair more than battery voltage. Unless you install an electronic voltage regulator the voltage will be set by the battery, and adjusting the third brush will change the amps being pumped into the battery.

500 engine RPM gives the generator 750 RPM.
 
If it is not hooked to a battery it can make over 40 volts for a short time----then it makes very low volts
 
Thanks everyone for the info. The battery was 5.8 and when I started the motor the generator was putting out 6.10. I was working on my turn signal's and that was why the battery was low.
 
Shortdog said:
Thanks everyone for the info. The battery was 5.8 and when I started the motor the generator was putting out 6.10. I was working on my turn signal's and that was why the battery was low.
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I only use an analog meter for Model A checks. 5.8 would indicate a dead battery for all practical purposes. Is you meter correct and calibrated?

At least you do indicate the generator is charging.
 
Tom Wesenberg said:
I only use an analog meter for Model A checks. 5.8 would indicate a dead battery for all practical purposes. Is you meter correct and calibrated?

At least you do indicate the generator is charging.
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I don't have an analog meter. Need to get one. My meter has never been calibrated but it is a good one. On the other hand I have only used it on a 12 vote system that has a alternator.
 
Tom Wesenberg said:
At 500 engine RPM a good generator should start to put out a hair more than battery voltage. Unless you install an electronic voltage regulator the voltage will be set by the battery, and adjusting the third brush will change the amps being pumped into the battery.

500 engine RPM gives the generator 750 RPM.
Click to expand...
Tom
You said adjusting the third brush. What is the third Brush? Also do you have an electronic voltage regulator on yours?
 
Here is a selected picture on the wiring diagram showing the generator. The third brush is movable to allow for different output.

To increase the output, you move the adjustable brush down.
 

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The third brush is located under the cover ring at the rear of the generator. The cover ring must be removed to see and adjust the third brush.
 
Shortdog said:
Tom
You said adjusting the third brush. What is the third Brush? Also do you have an electronic voltage regulator on yours?
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Yes, I always use a regulator, as it's so much better for the battery and bulbs.

Since few people actually move the adjustable brush, it may be stuck and require much effort to make it move. With the engine off try to move it by prying against the post, not the brush. Using the case opening as a fulcrum, and using a long screwdriver, you should be able to move it up or down.

The thinnest brush, between the output and ground brush, is the adjustable brush.
 

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Appears that the adjustable brush moves clockwise (in your photo) along the approx 90 degree arc between the output and ground brushes....yes?
 
Pilotdave said:
Appears that the adjustable brush moves clockwise (in your photo) along the approx 90 degree arc between the output and ground brushes....yes?
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Moving the brush clockwise in my picture would be downward on the car. This moves it closer to the output brush, which means it sends more voltage to the field windings, which raises the output current (amps).
 
It's easier to remember that to move the charging rate UP, move the 3rd brush holder DOWN, as you are looking into the mounted generator. To move the charging rate DOWN, move the brush holder UP. In other words, do the opposite of what you want the generator to do.
Marshall
 
As pointed out, the generator is really a current producing device. A voltage measured is a reflection of the resistance in the circuit (will battery).

The battery is the 'voltage regulator' for a factory Model A. A change in the resistance of the cells or in the connections to the battery will affect the voltage you measure.

Putting in Tom's regulator will control the voltage and the current and take some thinking out of operating the A's charging system. I would recommend that if you do not have a good understanding of electricity.
 
Thanks everyone for the info. if a person doesn't ask he doesn't get a answer. I don't mind asking. I have the red book coming. Has anyone thought about changing to a alternator.
Johnny
 
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