[Joe K]

The problem with the pre March 1929 vehicles is that the headlights were "type H" (i.e. glass lens with "vertical" ribs - a sort of carry over from the Model T) AND the headlights were designed to have a single bulb with TWO filaments. One filament (driving light) at 21cp brightness and one filament (parking light) at 3cp.

So yes, you need but two wires to go to the headlight socket.

BUT in March 1929, Ford changed over production to the "Twolight" system which includes a reflector with two sockets and three wires to each headlight.

The biggest difference between Type H and Twolight is in the headlight switch. The Type H switch has four rotating contacts inside, Twolight switch has but three.

In the Type H switch you have but three positions. One way is ON, one way is PARK and the middle is OFF.

In the Twolight switch you have four positions. One way is PARK, the other way is two orders of brightness LOW, HIGH. With the centerish position being OFF.

Today, unfortunately, all there is available in new parts is the Twolight version. It is possible to use a Twolight version complete - including changing the switch entirely to a 3 rotating contact switch - and cut off the two "park" wires headed to the headlights inside the switch. You still have four positions. Depending on the wire you abandon/cut you can have PARK-OFF-HIGH (spare)

Many have tried to use a Twolight wiring harness with a Type H switch. It doesn't work for a variety of reasons - and may result in a short circuit.

My truck is July 1928 and I'm looking for a Type H switch. They're out there but not common. The Type H harness is actually harder. I have a friend who does computer "printing" and can make wiring plates. I'd have to come up with "contacts." And wires could be a Twolight wires de-soldered.


Right now its a work in progress.


Joe K