Confounded by even the simplest electrical problems

[Richard F]

I am never comfortable with even the simplest elecrical problems and could use some advice.

I have a '34 classic with third brush voltage regulation and 6-volt positive ground electrical system. About a year ago I had the generator rebuilt and afterwards it was set to charge at about 20 amps (as shown by the car's ammeter). I know the third brush is adjustable to vary the charging rate but I just left it alone after the rebuild--partly becouse I figured the generator shop knew more than I did and partly because I don't know how to adjust it. After the rebuild, the car always showed a charge when runnning-- even a 4-5 amp charge when the lights, five-tube radio and heater fan are all on. It has not overcharged the battery (at least not enough to cause a battery boil-over) although I have not driven it long distances.

Recently I replaced the head and tail lamps with 6-volt halogen bulbs that I ordered from a guy that makes them in Australia for antique cars (http://classicandvintagebulbs.com/index.html). I had hoped to improve the light from the old non-sealed beam head lights and ended up replacing all of the bulbs. For a while it did just that. Then in a matter of days, one by one, both head lights burned out and one of the tailights I had installed. I reinstalled the old tungsten bulbs and things are back to normal except for one remaning halogen tail light bulb, which continues to work fine.

I suspect that the halogen bulbs are more sensitive to the voltage fluctuations that occur in this old system and that may be why I burned them out quickly. It's also possible that the charge rate on the third brush is set too high.

Does anyone have some thoughts on what has happened? How simple is adjusting the third brush on the generator to lower the charge rate, if this is contributing to the problem?

[Guest]

Adjusting your third brush generator is as easy as falling off a log. Open the band cover on the generator. The third brush should be redily visible. It is the one that has a slot headed machine screw sticking out of the end plate next to it. Loosen the screw a half turn and slide the third brush either up or down to change the charging rate. If you have the engine running and use your finger (carefully) to move the brush holder around you can have someone sitting in the car and they can tell you exactly how much you have changed the rate. Otherwise move the brush holder, tighten the screw and start the engine to check the charging rate. You might want to consider installing a 6 volt alternator??

Happy hobbying.