MTFCA Forum

So as to NOT steal 1925 Touring's thread, I started this thread.

IF LED light bulbs are rated in 6 and 12 volts on a Battery, Generator, or Alternator, What bad results are to be expected when running them on the Magneto voltage of up to 30 volts AC?

I have 6 volt LED bulbs in front marker lights and rear marker/stop lights. They appear to operate normally as far as I can tell, but I still worry about the higher voltage from the magneto damaging them. I have not upgraded to LED headlights yet.

Thank you for your input. I hope this thread will help others when they are thinking about LED lights.

Seeing that you do have several Model T's , do any of them have electric headlights that run off the magneto?.. the LED bulbs will work with no problem on 6 volt or 12 volt battery/ generator power. Magneto headlight bulbs are wired in series and markings on original bulbs they can be used at voltages from 6 to 8 . ... Guess there is something you have to look into.

Most LED bulbs for automotive would-be DC not AC. You would have to know if they can operate on both and if could handle the variable range of voltage. Battery would for example be 6 volts DC and supplies a more or less continues current and light output, where-as the magneto would be all over the place.

I spoke to one of the vendors a couple of years ago about this very thing. The reply was that in theory the fancy bulbs that do not require focusing may, I stress may work. The bulbs were rated for 6-25 volts ac or dc. Expensive experiment for sure.

Brian, Thank You.

Those are the specs. I was hoping for. I know some LED bulbs have a rectifying circuit in the bulb and are able to use AC or DC and the voltage range is within reasonable amount.

If you want to experiment with the headlight LED bulbs, better (lower) prices can be found elsewhere besides the T parts catalogs.
https://www.ledlight.com/6-volt-negativ ... ights.aspx

Correct me if I am wrong, but aren't the lights, horn, and starter on a DC circuit?
The magneto is only wired to the coils on an AC circuit.

So LED headlights never get a taste of AC current.

DHort wrote: ↑

Sat Jan 27, 2024 10:22 pm

Correct me if I am wrong, but aren't the lights, horn, and starter on a DC circuit?
The magneto is only wired to the coils on an AC circuit.

So LED headlights never get a taste of AC current.

Except for non starter cars,
one would have to specifically wire off the magneto line to the bulbs and would need to really plan it out to keep the Magneto power stays isolated from the rest of the electrical system. Would need to use a totally separate set of wires & light switch.

DHort wrote: ↑

Sat Jan 27, 2024 10:22 pm

Correct me if I am wrong, but aren't the lights, horn, and starter on a DC circuit?
The magneto is only wired to the coils on an AC circuit.

So LED headlights never get a taste of AC current.

Non-starter cars (no generator too) depended on magneto. A dimmer was located behind the blocking plate where the Ammeter would have been. Models with the ignition switch on the coil box had a dimmer on the firewall --
--
The magneto voltage also varies with engine speed. Would be interesting to see how a variable voltage, AC/DC LED would react