Distributor Rotor
A spinning electrical contact inside the distributor cap that distributes high-voltage spark to the individual spark plug wires.
The distributor rotor is a key component of older ignition systems. It is mounted on top of the distributor shaft, which is driven by the engine's camshaft. As the shaft spins, the rotor rotates inside the distributor cap, receiving high-voltage current from the ignition coil and distributing it to the contact points of the spark plug wires in the firing order.
The rotor features a metal contact tip that passes very close to, but does not touch, the cap terminals. The high-voltage spark jumps this small gap, flowing through the plug wires to ignite the air-fuel mixture in each cylinder at the precise millisecond required.
Over time, the electrical spark causes erosion and carbon tracking on the rotor tip and cap contacts, increasing electrical resistance. Worn rotors and caps lead to engine misfires, rough idling, hard starting, and ignition codes. Replacing the distributor cap and rotor together is a standard part of a tune-up on older vehicles.