Reply To: Correct amperage output?

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Hello Mike,

I went back to the reference material and I show that the Maximum charging rate for a cold Series 81 generator is 24 Amps at 1600 RPM. A couple of other data points are given as normal operation:

5A @ 800 RPM

11A @ 1000 RPM

15A @ 1600 RPM with 7.5V – 8.0V output

Based on this data, your observations of current output appear to be in the ball park. You can adjust the current output of the generator by moving the 3rd brush position inside the generator. You gain access by removing the commutator cover band on the body of the generator. Shifting the 3rd brush in a counterclockwise direction increases the charging rate. Moving it the opposite way decreases the charging rate. The brush is usually secured by an adjustment screw. If you are seeing 20A, you could lower the output a little by moving the 3rd brush to take some of the load off of the system. Unless you are running extra lights or electrical accessories, getting every last amp of output from the generator is not that important, especially since your car was not built with voltage regulation or overcharging protection for your battery.

I have had one generator fail, similar to how you described by the cutout relay failing, sticking closed, and allowing the battery to discharge through the generator. This ruined the battery and heated the generator to the point where it had flung its solder and discolored the windings. Verify the action of your cutout relay that it definitely is disconnecting the battery from the generator, say at idle, when the generator output is reduced, or when the engine is stopped. There should only be battery voltage on the battery side of the cutout relay and the generator should be isolated. I have seen large diodes successfully installed inside cutout relay bodies to eliminate the electromechanical relay action and replace it with a solid state diode.

I assume that the bearings in the generator were replaced when your generator was rebuilt. If you have sealed bearings, which are permanently lubricated, you don’t have to worry about filling your generator oil cups anymore. If they used non-sealed bearings in your generator, they will continue to need lubrication through the oil cups at each end of the generator. Dry bearings will generate heat, but their failure will usually be accompanied by noise or seizing.

Good luck with resolving your generator questions.

Happy Motoring,

Chris