Rotor Arms: The Spinning Contact Inside the Distributor

The rotor arm sits at the centre of the distributor, rotating with the distributor shaft. As it rotates, the rotor’s tip passes close to (without touching) each cap contact, transferring the high-voltage spark from the coil to the correct cylinder’s plug lead.

How rotors fail

Tip erosion — the spark gap between rotor tip and cap contact erodes both surfaces over time. Eventually the gap becomes too wide for reliable spark transfer.

Carbon tracking — carbon residue from sparks builds up on the rotor body, creating an unintended conductive path that lets spark leak to wrong locations.

Replacement

Always replace rotor and cap together; usually replace at the same time as plug leads on a major ignition service.

Brand

Bosch, NGK, Beru, Marelli cover OE-equivalent rotor arms.

Find rotor arms for your engine on the Rotor Arms collection.