Six volt Sunday

Posted by Ross On 2023/4/29 19:25:45

There are quite a number of 6 volt cars around me, and being a contrarian I love to go and start them up in cold weather and when they have been sitting for a long time. 'cause they do. But I do know the difficulties that people have and I know the troubles my customers bring me. As noted in another thread, clean connections and good cables are a big help.

But here is what I noticed lately and now I am on a search and destroy mission. My low mileage 50 Commander (Delco system, just like a 50 Packard) has always started quite OK, and shows a good charge on the ammeter, keeps its battery up, etc. But the headlights were wretched and the dash lights though not sunburnt were dim. They are the glowing type, like 22-23d series. For grins I tossed a voltmeter across the battery while it was just sitting and saw only 5.7v. A standing 6v battery should read about 6.3 just as a standing 12v battery should read 12.5 or so. So I cranked the old girl up and discovered that she was only putting 6.4 volts across the battery at the best. Charging voltage is supposed to be 7.2-7.4 volts. (14.4v on a 12 volt car)

Inside the regulator of most any of those generator equipped cars are three relays. One disconnects the battery from the generator when you turn the car off, one limits the total output so the generator does not commit suicide, and the third regulates the amount of current to the field which in turn determines what voltage the genny makes. That one is a magnetic coil in a sort of tug of war with a spring loaded contact. Contact closes, voltage goes up. Voltage too high the coil tugs it open. All that to say one adjusts the spring tension to adjust the voltage. Older Delcos elegantly have a little screw to do this. Others you have to bend the spring hanger.

So with everything well and truly warmed up I put the 50 on a good high idle, turned the parking lights on and then set my voltage to 7.5. The voltage drops about.2v when you put the cover on the regulator because of some magnetic effect, so I ended up with 7.3 all done. It took a long drive to bring the battery up to its new correct baseline. But now the car leaps to life when I punch the starter and the 73 year old sealed beams are as they should be--as is all the lighting.

Checking through inventory I am finding voltages all over the place, but none too high. My 41 was only .4 v low, but adjusting made a nice difference. I suppose that over the years the regulators are losing spring tension and the contacts do erode from constant action. So with a quarter turn of a small phillips screwdriver you can bring the car back to standard condition with very pleasing results. Try it, you'll like it.


Just to underline: go for a drive and get everything warmed up. Set the idle up nice and high, put the parking lights on to make a little load. Set it to 7.4 and let it run for a few minutes to stabilize. When you put the cover back on the regulator it will drop to 7.2. The ammeter will of show a moderate charge at first, but after the battery has come all the way up the needle will go back to the middle. My 50 was charging at about 10 amps at first as it had a lot to make up. If the ammeter continues to show a heavy charge something is wrong and you need to go back and recheck.