MTFCA Forum

I am putting a 6 volt alternator in my 21 touring. In looking in Lang’s catalog they list a separate ammeter for use with a alternator. Will the one in my switch plate work or will I to change it?

It should work. I put a 6V alternator on my 25 Fordor last fall and it's been working fine.
It usually shows around 6-8 amp output right after I start the engine, then quickly falls back to 1-2 Amos while running, even with headlights on. So nice!

Ammeters can be used with alternators provided that they are within range of the amps to be consumed by the vehicle. So if you don't have a lot of electrical stuff connected then a 20 or 30 amp gauge should be okay.
About the 6v alternator that Lang's sells "The Delco alternator is rated at 70 amps when used on a modern car. It will easily produce up to 20-35 amps on the lower RPM Model T engine." So the real question is - How much amperage do you think you need? Lots of amps also require heavier wire.
Good reading - https://fifthaveinternetgarage.blogspot ... ts-vs.html

There must be a reason why the dash board instrument went from an ammeter to a voltmeter when vehicles went from generators to alternators.

I have always suspected it was the increased cost of a meter to run more current through.

I have helped several people with alternators replacing the Model T generators and I have not seen one yet that would produce more than 35 amps at 35 mph on the highway.

We bought an "Off Topic" car some years ago in which some of the components were swapped from 6v to 12v and there was an alternator in place of the generator. We replaced the remaining items with 12v compatibility and replaced the non-working alternator but the parts store handed us a 90amp alternator. The 10ga original wiring has held up to the current for over a decade now but I was concerned with the ammeter early on and jumped the two terminals with a 14ga copper wire to help carry the load and not burn up the ammeter because I did not know its limits. I cannot give you specific electrical safety advise, just reporting what has worked for us.

The reason that auto manufacturers switched from ammeters to voltmeters was because the A C generators were capable of putting out much more current then the standard generators. This would have resulted in having to install much heavier-duty (and expensive) ammeters. The same low-voltage voltmeters would work and be cheaper. Although the A C generator does in fact, generate A C, by the time that the current leaves the A C generator it has been rectified to current that for all practical purposes looks like D C. As long as the D C voltmeter has a range consistent with the generator output, it could care less what is going on inside the generator.

Then too, the ammeter only measures current, so it could care less about the voltage amount.

The old E = IR and W = EI formula suggest that for the same electrical power requirement the current can be halved.

The lower current requirement allows for a large savings in smaller copper wires.