A reluctor ring is a notched circle used in the anti-lock brake system (ABS) and the ignition system of cars. The anti-lock brake reluctor rings are located on each wheel. The distributor-less ignition, or direct-ignition, reluctor ring is mounted on the crankshaft that triggers the magnetic sensor. The ignition reluctor ring combines evenly and unevenly spaced notches that send information to the electronic control module in order to control ignition timing.
A warning light will notify the car owner if the ignition reluctor ring needs to be replaced. If a car needs a new anti-lock brake reluctor ring, then the ABS system lights may flash on and off. Banging might also occur when braking at slow speeds, or the brake pedal may fluctuate.
There is no need to replace all ABS rings at once. To find the cracked ring, a mechanic uses fluorescent fluid and an ultraviolet lamp. About an hour is needed for a qualified mechanic to replace an ABS reluctor ring. Replacing the ignition reluctor ring takes a full day because the ring is connected to the crankshaft.