Part I


By E. Meloan

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

Howdy, fellow Model T’ers! I’d like to spend a couple of articles discussing the Model T electrical system and problems that can keep our car from getting us out on the road!

The 1909 through 1914 T’s have a very simple system. Two wires are attached to the coil box to provide electrical current. Looking at the box from the front of the car, the post on the lower right has a wire that connects to the magneto terminal on top of the hogshead (transmission cover). The post on the coil box is connected through a wire inside the box to the Magneto side of the coil switch. Located on the lower left of the coil box is the battery terminal which was usually hooked to the positive terminal of a six volt battery or a group of six lantern batteries to provide current for starting the car. An internal wire inside the box will connect this post to the “Battery” side of the coil box switch. A third wire goes from the switch down to the copper strip on the bottom of the coil box which contacts the button on the bottom of each coil to provide the positive voltage.

Four wires are attached to the row of posts along the top of the coil box which connect to the timer (commutator) Again, looking from the front of the car, the left wire should go to the post on the timer that is grounded when the spark plug in number one cylinder fires. The second post from the left is cylinder two. The third three and the forth, cylinder four. The actual firing order for the “T” engine is 1,2,4,3 so we must be remember to reverse the wires on the timer for 3 and 4!

Add four high tension wires which go from the lower row of posts to the spark plugs and you have the total wiring system for a pre-1915 T!

While six volts will start the car, it is not enough voltage to operate the coils well at speeds above about 20 miles an hour. So, you turn the coil switch to the “Bat” side to start on battery and when the engine is running, move the switch to “Mag” for driving. A good magneto will put out 20 to 30 volts and make the coils really sing!

The electrical problems with the 09/14 system were pretty much limited to loose connections or shorts in the commutator wiring and coil problems.

Probably the most likely spot for trouble is the commutator and commutator wiring. I’d be hard pressed to think of a worse location for a timer than the one on a “T”! It’s not easy to get at, it gets wet and coated with oil and the connections are very close to things that can short them out!

Looking again from the front of the car, the commutator contact at the 11 o’clock position will normally be number one. The timer rotor turns counter-clockwise so the number two contact will be the one at 8 o’clock. That takes care of the two contacts on the left side of the timer. The bottom right contact (4 o’clock) will have number 4 (NOT 3) because 4 fires BEFORE 3. And the contact at the 2 o’clock position will connect to the number 3 coil.

Common problems are timer wires that have broken off from the continual flexing and wire connectors on the timer contacts that touch the timer advance rod as it moves through its arc. Also check for pan bolts that can short out the lower contacts on the timer case.

If you remove the sparkplug wires from the plugs and switch on the battery, each coil should buzz as you hand crank the engine slowly. Disconnecting the sparkplug wires can save you from a broken arm should there be a short that makes a coil fire when its piston is in the wrong position! You can quickly check your timer wiring by shorting out each timer contact to the timer case with a screw driver and checking to make sure that the proper coil buzzes with the proper timer contact.

One last thought… Not all timers fire at the same position! The little tool sold to set timing by the “T” suppliers was meant for the original Ford timer. NOT for the New Day or the Anderson timer! We’ll continue this discussion in the next newsletter.

See you down the road…