Generator Overcharging

dpson

dpson

Senior Member
When running my 1931 Model A the ammeter pegs on the charge (+) side, so it appears to be overcharging. How do I adjust the generator to turn down the charging rate? It's running a modern (electronic) cutout.
 
Remove the band and move the adjustable brush up, or counter clockwise when look at it from the front of the car.
 
What others are talking about is adjusting the 3rd brush which controls how much current is delivered to the field windings and in turn how much the generator generates. Also, if the connections to the battery are not good the generator voltage can increase to 20 volts or more.

Search for Model A generator adjustment or 3rd brush. There are some videos on YouTube on how do adjust the 3rd brush.

There are voltage regulators that mount to the inside of the band if you want to go that route.

It is also possible that there is something wrong with the battery so that it does not charge to develop full voltage and is therefore looking for more current. Check the electrolyte level in the battery.

It is normal for the charging current to be high when first starting the car as it is charging the battery. Once the battery becomes charged the current should fall to 5 to 10 amps.
 
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one of the generator brush mounts is adjustable on both the powerhouse and newer type model a generators. this is called the third brush. you loosen the lock screw on the brush mount a bit then move the mount to change the charging rate.
 
Thank you for the responses. I'll give the electrical connections a check and will charge the battery, as this was the first outing after sitting all winter, before making any adjustments to the generator brushes.
 
I had a cut out failure with an electronic cut out. According to NewRex theirs is the only one with enough heart sink capabilities to keep it cool and lengthen its useful life.
 
AND If you have a voltage regulator disguised as a cut-out, you probably don't have a problem - other than low battery.

The "free voltage" of the Model A family of generators can be as high as 32volts. The point of moving the brush is to bring this down to the proper amperage (i.e. that found at perhaps 7.5 volts) to charge the battery. The point of a regulator in disguise is to REGULATE the voltage - so this is probably the best solution as it tends to get past "connection issues" when they exist.

Vince's page (and section) is worth reading - and may describe the symptoms you are experiencing.

Vince's (Tom Wesenberg's) writeup found at https://www.fordgarage.com/pages/powerhouseregulation.htm starts out with discussion of the Powerhouse Generator, but about half way through morphs into voltage regulation.

Tom's expertise (and VRs integral to the case) will be missed. I only recently caught on to the fact of his passing back in February.

Joe K
 
With the heat sink mounted inside the can, it's likely that it's effectiveness may be lacking. An aluminum heat sink does better if it's out in open air but that may not be practical in this environment. A large power diode should work well enough if it's of a value to take whatever comes to it.

It is very important for the battery and it's cables be in good fully charged condition with clean and tight terminals. The battery is the only thing that regulates the voltage so the best connection possible to it is very important.
 
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rotorwrench said:
With the heat sink mounted inside the can, it's likely that it's effectiveness may be lacking. An aluminum heat sink does better if it's out in open air but that may not be practical in this environment. A large power diode should work well enough if it's of a value to take whatever comes to it.

It is very important for the battery and it's cables be in good fully charged condition with clean and tight terminals. The battery is the only thing that regulates the voltage so the best connection possible to it is very important.
Click to expand...

Opening the can on a NewRex invalidates any warranty. What would be a suitable additional heat sink?
 
I'd go for a working or repairable original type electro-mechanical cut out. A good power diode will work but I just like the old original type stuff. When diodes give it up they generally just go open circuit but sometimes they will pass current both ways which is not good. If a person purchased the correct power diode then they can replace it if it blows out. They are comparable to the ones used in modern alternators.

No one is currently marketing the voltage regulators for the 3-brush. There may still be at least one person making them one at a time but they aren't available from the model A parts sources.
 
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Check out my video on adjusting the generator's 3rd brush. It clearly explains how to do it.

https://youtu.be/PL94VX3GIq8

Also, I sell refurbished, tested and adjusted original Ford cutouts.
 

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You may also want to check your electrical connections in the charging circuit. I had the same issue and thought it was my generator and found 2 loose connections. One was at my Amp gauge and the other was at my terminal box. Went from 16 volts to 7.
 
i made my diode cutout by taking out the center core and windings, drilled a hole in the relay frame and pressed in a used first generation delco alternator diode, that has been enough of a heat sink to last over 40 years at a 14 amp or more charging rate.
 
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