The distributor was the heart of a car’s ignition system for nearly 100 years. Today’s automobiles forgo the distributor. Emissions-control requirements spurred the use of electronic systems starting in the late 1970s, but the breaker point ignition utilized by the trusty distributor is still on board many cars today. The distributor is a study in simplicity and the brilliance that it sometimes displays.
The shaft looks like a post holding the rest of the distributor in place, but it is actually more of an axle with a cam attached that turns hundreds of times per second when the engine is running. The cam opens the breaker points as it turns.
Just like a breaker in your home electrical box, the points open and close to alternately block and allow electrical current. When the points are closed, current passes freely to the ignition coil. When they are open, current to the coil is interrupted, causing the magnetic field to collapse. This collapse sends high voltage back to the distributor and the rotor inside.
The rotor, charged by the voltage coming from the ignition coil, spins inside the distributor cap, sending the charge via a small gap to the high tension-wires connected to the cap. This happens in sequence for each of the wires, thousands of times per minute.
The distributor cap houses the contacts that conduct the electrical charge and send it to the appropriate wire. The number of wires exiting the cap is equal to the number of cylinders in the engine. Each wire leads to a spark plug that ignites the fuel in one cylinder.
The electronic module replaced the points. It performs the same function as the points, but much more efficiently and without the required maintenance of the standard mechanical points.
