Saab 900 Distributor Rotor Arms From Jan 1979 to Dec 1993 Available Here. Your vehicle’s ignition system is responsible for getting your engine going, and to do that, you need to have working distributor rotor arms. Once your car’s distributor receives the electric currents from the ignition coils, the rotor arm inside the distributor spins past power points on the distributor cap. As it spins, the rotor arm sends the voltage out through these points to the spark plugs located at each of your engine’s cylinders, where that voltage is finally used to ignite your car’s fuel. If your rotor arm fails, your car’s ignition system falls apart. Make sure your engine starts by having the best distributor rotor arms for your vehicle.