Part II


By E. Meloan

(This article was originally published in the May, 2003 issue of the Spark Coil.)

In our last column, we began a discussion of the electrical system of the Model T.  We talked about the very simple system used on the 1909 through 1914 models.  Now let’s move on to 1915…

In 1915 Ford finally gave up on Acetylene headlights and a kerosene tail light.  The “new” 1915 Ford sported real electric headlights!  Still no electric starter but a giant step forward in safety and convenience over the older lighting system.  But the “new” Ford still did not come standard with a battery.  The headlights had to get their power from the engine magneto.  To supply the additional current needed for the headlights, Ford beefed up the magneto so it could power both the engine and the lights.

This was not an ideal arrangement as any Ford owner of the period would quickly tell you.  Since the speed of the engine governed the amount of voltage put out by the mag, the lights also got brighter or dimmer according to the engine speed.  When going slowly, the light was barely sufficient to see the road and when you got up to a higher speed, it was not unusual for the bulbs to burn out!  Not a happy situation on a dark country road. To try and improve this situation many third party suppliers sold “equalizers” which were supposed to control the voltage and increase bulb life.  Ford even came out with an “equalizer” circuit of their own.  These may have helped bulb life but the system was still a poor one and it was obvious something better was needed.

Lets talk a little about the wiring used in the Magneto lighting system.  If you look at a bulb made for the mag system, it looks very much like the two filament bulbs used in later years.  That is, it had two contacts on the bottom.  But the resemblance ends there.  The headlights were actually wired in series rather than each light being wired to ground.  This meant that current flowed from the switch through the first bulb contact in the passenger side light and then through the filament and then out the second bulb contact through a wire along the bottom of the radiator and in to the first contact of the driver side bulb.  After going through the filament, current flowed out through the second contact and through a short wire to ground.  Folks restoring this system sometimes find it confusing since they are used to the later grounded bulbs in every socket.

Now might be a good time to discuss magneto problems since the magneto is so important to the 1915 through 1919 cars lighting systems.

A good magneto should put out about 6 volts at a good idle and range upward to 25 to 30 volts at higher engine speeds.  If you want to measure your magneto output, use an analog voltmeter and not a digital one.  You are measuring a voltage that increases and decreases as each magnet passed the stationary coils in the magneto so you will want to use the AC setting and NOT the DC one normally used for testing a later automobile battery system.

If the output is lower that it should be, the first area to check is the magneto terminal post on the top of the flywheel housing.  This contact uses a small spring to contact a solder point on the top of the magneto coil assembly and there is a tendency for band lint to build up at this contact and too much can cause poor conduction with the resulting loss of voltage.  If you are lucky, removing this contact and cleaning it may  give you back the voltage you are missing!

If the contact is clean, then there can be several reasons for low output.  If you have some voltage but just not enough, it is likely that the magnets have lost their magnetism due to heat and vibration over the past 80 years or so.  It is possible to remagnetize them in the car.  While not as good as removing the engine and remagnetizing each individual magnet, doing them in the car does not require removing the engine and can make a poor magneto work until an engine overhaul.  We’ll talk more about this in our next column.  Until then,

See you down the road…