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140: Jeff Johnson, “Voltage Professor”, 6 or 12 volt? Positive or Negative Ground?

Show Date: 04/08/2017

(Show Notes and Links at bottom of the page)


Jeff Johnson

AlStar Company, LLC

In the age of “take out and replace it” with anything that is electrical on a vehicle has taken its toll on finding anyone who can simply fix it. It’s difficult to have someone rebuild a generator for a 1928 Bugatti that is being restored for competition. What about restoring a 6-volt system on a 1950 Ford or should it be upgraded to a 12-volt system? Maybe you want to convert your generator to an alternator but you prefer to keep the look of the old generator to appear original equipment.

Jeff hasn’t given up on those tossed and forgotten electrical parts. He has been working with alternators, starters, batteries and cores for decades.  Whether they are on automobiles, motorcycles, semi-trucks, tractors, giant earth movers – from extremely large to tiny applications – Jeff can evaluate any electric system and provide appropriate solutions for maintenance or repairs.

Car builders from around the world reach out to Mr. Johnson requesting his services or advice. He receives alternators or generators from places like Australia and Denmark where they love their automobiles and what to make sure it’s all original. Owners of antique motorcycles send their parts to him for complete rebuilds or repairs.

So tune in the hear from a rare “Voltage Professor” – Jeff Johnson.

AlStar Company, LLC
24023 Burmeister Road, Union Grove, WI


Alstar Company is a partner of Midwest Service Equipment

Wisconsin Hot Rod Radio is not being compensated for this interview. We are always looking for items that car guys would need. “The Voice to the Hot Rodders”.


Podcast Notes and Links:

Yesterday, Friday, April 7th was officially the 10 Year Anniversary of the Wisconsin Hot Rod Radio show!!!!!

Jeff Johnson from Alstar Company

Jeff works with all kinds of automotive electrical systems, 6 volt, 12 volt, positive ground, conversions either way 6 to 12 and then restore back to 6 if you would like.

Jeff is available to service any electrical systems whether you have bought the parts from him or another shop or even online.

In the 60’s, the performance cars came with the smallest alternator possible to save weight. Alternators can have a charging curve where it charges at a lower amperage at idle but increase as revolutions grow. A 60 amp alternator may be enough when people go looking for the 100 amp set-ups.

A correctly running and wired 6 volt car can work perfect. A 6 volt system may need a cable twice as thick to move the electrons that a 12 volt may in another wire but it can work great if everything is running correctly.

When converting from a 6 volt to 12 volt you need to consider the whole system. Will you be going from generator to alternator? On the generator systems, once the car is started, the generator takes over and then tries to charge the battery. On an alternator the system runs off of the battery and the alternator tries to keep it charged. How these 2 systems run can make a difference on the components of the whole electrical system. (I hope I got this right – to make sure, listen to Jeff and contact him if you need help).
The difference between positive and negative ground? Listen to Jeff in the podcast.

Converting a 6 volt car to 12 but still want to run your 6 volt gauges? You can get the new solid state voltage reducers and it should last the life of your car.
Old Chryslers get ceramic ballast resistors to help save the points in the distributor. There was a lot about the lower voltage needed to fire the points but you’ll have to listen to the show. Newer electronic distributor conversion systems don’t need the reduction anymore.

Rebuild vs buy new for components? Have you heard about the hot hard start problem on GM big-blocks? If you keep using rebuilt starters remember that the copper in those starters can wear out even though it passes the tests. Those starters are getting old and may have been rebuilt more than once.

When you have an old car, rebuilding/restoring the old part is an option. When you want to keep it all original, Jeff can put all new guts in the old casing.

Jeff will be attending and displaying at the upcoming Wisconsin Hot Rod Radio Anniversary show.

Jeff likes to wear odd ports coats as he and his family are into older sports cars – the ports coats come in from Dustin Hoffman in the graduate as he dressed strange while driving around in his Alfa Romeo Duetto in the movie.
Alstar Company, LLC
24023 Burmeister Road
Union Grove WI 53182