12 Volt generator cut out

SteveB31

SteveB31

Well-known member
So.....if you convert the stock Model A Generator to 12 volt negative ground. What do you use for a cut out?
 
It's just an electrical gate that prevents the battery from turning the generator like a motor when the car is off. Power goes one way, from the generator to the battery, when the car is on. The cut out opens when the car is off, so that battery current doesn't run backwards to the wiring in the car, potentially causing a fire.

Great article: http://modelabasics.com/Cutout.htm
 
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The diode cut out is another animal, you must have the correct polarity and voltage, it cares.

Mind you, I am not an expert, but I have seen other folk let the smoke out of the diode cut out when it was not the correct polarity. Once you let the smoke out, they don't work.
 
Yep, the cutout is just a switch. An extra 6v isn't going to bother it, that is, it its a good original. An aftermarket diode type probably will not like what you're doing, they get fussy about polarity.
 
RawhideKid said:
The same one you were using for the 6v pos ground cause it don't care.
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Actually the stock cutout does care, it is made to close at 6-7 volts, a diode cutout only cares about polarity, the generator will "charge" anytime the generator votage is 1/2 volt above the battery voltage

the generator field coils care , they get quite hot when the generator is making 12 volts( I don't know what the final running temp using 6V fields on 12V, I shut the test down at 220 degrees, I had a thermocouple wedged next to the field coil for the test)---on 6v the field stayed below 120
 
So, apparently the answer is buy a 12 volt negative ground voltage regulator or a negative ground diode cutout. Thanks guys!!!

I knew a regular original cutout would not work, and I knew. Diode cutout made for positive ground would not work.
 
It's not hard to make your own diode cutout. You can get diodes for either positive or negative ground. It doesn't regulate though.
 
A diode cutout and a regulator are two separate and different things.

The diode does care about positive and negative ground but the ones used for the A's don't care about voltage. As a matter of fact, the most common diode used for positive ground systems is rated 35 Amperes and 200V without a heat sink.
 
SteveB31 said:
So, apparently the answer is buy a 12 volt negative ground voltage regulator or a negative ground diode cutout. Thanks guys!!!

I knew a regular original cutout would not work, and I knew. Diode cutout made for positive ground would not work.
Click to expand...




There are many original cutouts out there being run on 12v. If you want to get rid of yours, I'll take it. :)
 
Lots of cars out there that have just been switched to 12v neg gnd only changing the coil polarity, ammeter polarity, and bulbs (and of course battery). Not what I would do though. I like the idea of a voltage regulator, I run quite a bit of night driving so don't want to be always adjusting my 3rd brush, otherwise your either killing or cooking your battery. Bad deal either way. Unless you have a specific reason to switch to 12v, I would suggest leaving it at 6 volts.
 
SteveB31 said:
So, apparently the answer is buy a 12 volt negative ground voltage regulator or a negative ground diode cutout. Thanks guys!!!

I knew a regular original cutout would not work, and I knew. Diode cutout made for positive ground would not work.
Click to expand...


Hey Steve, call John Reagan. Like Andy was saying to Aunt Bea, "Call the man, ...Just call the Man!"
 
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