MTFCA Forum

Working on a 16 cutoff touring for a fella. The car has been layed up in a shed since WW2. It has this coil? installed in line from the mag to the switch. Guessing it was to up the power to the headlights. Was this common? Did they work?

It is a headlight dimmer. Introduced in about 1918. It is actually a resistance unit. The headlight switch for that era has two "on positions. One for dim and one for bright.

The headlight run off the magneto. Just like you old bike light generator, the faster you ride, the brighter your headlights are. However, when running the engine fast, it will generate too much voltage and Boof! your bulb burns out. Since they are wired in series, both lights go out. So when running fast, you could dim the bulbs and prevent burn out.
Here is the back side of the combo horn-headlight switch.

I'm not sure why/how it is wired in with the 1916 pull/push headlight switch.

: ^ )

Keith

Might be a dimmer coil. The 1915/'16/'17 Ts used a simple magneto powered headlamp system.The problem was that if the engine was running slow, the headlamps were very dim. If rpm went up to a cruising speed,the lamps were nice and bright. However,if rpm went up too much, blowing out a bulb became a real possibility, and because the lamps were wired in series, if one bulb blew, both lamps went out. About 1918, Ford went to a two"on" position switch,and a dimmer coil to drop the high AC Voltage down and not blow bulbs. Someone may have adapted such a dimmer coil onto the earlier car. Ts with a dimmer coil continued well on into the '20s on the no starter/no generator models. Original dimmer coils are a bit tough to find these days!

Keith types faster than I do!

Early ones (15/16) didn't originally have the coil - they were a simple push/pull switch on the dash, Mag to Switch to headlight wire. Wired in series, you were ok unless you really overspeeded your motor. Of course, if one goes out, they both go out. But in series, with the 9 volt "Ford" bulbs, it would take 18 (or 28) volts. I have a stash of NOS 9 volt headlight bulbs, and also have the taillight wired with a 28 volt aircraft bulb (because those darn taillights like to blow out at speed) into the circuit.

I always thought the resistance coil was added on when they put the metal dashboards on the cars... the mag bulbs were direct, either 9 volt series or 18 volt parallel wired.

Resistance coils were used with the combination horn headlight switch that had two on positions, whether there was a steel dashboard, or instrument panel or not.