In Reply to: Generator not charging on 6 V 49 8N posted by KY Dave on June 01, 2013 at 23:05:22:
If your generator is stock for 1949, then the generator is a type 8N100000B, like the one I have.
There are four different wiring configurations and six different models, so it gets rather confusing.
According the manual the resistance of the F terminal to ground should be 3.2 ohms for the model 8N100000B & 8N10001. The model 8N10001 was used after 1950
An easy method to check if the generator works, is to convert it from a generator to a motor.
1.Disconnect the A & F terminals from the VR.
2.Jumper a wire from the + battery terminal to the A terminal with an
DC amp meter with clips or just a jumper wire without the DC amp meter.
3. Jumper another wire from the F terminal to the generator case.
If the generator runs it will produce voltage and current to charge the battery.
The amp meter is used to check if the current > 8 amps.
There have been some rather heavy duty discussions in the past on polarizing.
The generator must be properly polarized to charge the battery ,so the current travels in the correct direction. If the generator is not polarized correctly, the field windings can burn up when the generator is spun by the engine belt.
Every time the battery is disconnected from the generator it is recommended to polarize the generator before the generator is spun from engine power.
The generator can actually be polarized using four small dry cell batteries in series to produce 6 volts. If you feel lucky, the 6 volt wet cell battery can also be used having the larger current capacity.
Over the years the stock generator can be changed out to another type ,so it is really important to identify the model of generator, first.
If your have a 49N stock 8N10000B generator, the generator is polarized by connecting a momentary jumper wire between negative terminal of the battery and the F terminal on the generator with a positive ground setup. The positve side of the battery must be connected through the chassis or directly to the generator steel housing.
Voltage regular
Then there is the VR. The original VR has a screw to adjust the spring tension on the vibrating voltage regular. The spring tension is adjusted so the generator supplies current to the battery when the generator output voltage is between 7.1 to 7.5 volts on the generator model 8N10O00B and 8N10001. Other models have a different settings.
Gassing Voltage
Wet cell lead acid batteries have characteristic called gassing voltage. When the charging voltage is greater than the gassing voltage the acid boils out of the battery. The problem is on a hot summer day of >100F the charging voltage is greater than the gassing voltage and the acid boils out of the battery. That is why on the old charging setups the operators were always adding water to the batteries.
I gave up on the 6V generator with all the headaches and use one yellow top OPTIMA 12 volt deep cycle, 48 amp-hr capacity AGM battery in conjunction with a 12 volt front mount coil with negative ground and a full time three step float charger, when not in use.
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