Bosch Hall Effect Electronic Ignition

The Bosch Hall Effect electronic ignition system consists of an ignition coil, distributor with Hall Effect sending unit. Hall ignition control unit, vacuum and centrifugal advance mechanisms are present on some models.

The Hall Effect sending unit in the distributor receives voltage from the knock control unit or directly from the electronic ignition control unit. A trigger wheel (shutter blades), mounted on the distributor shaft passes in and out of the air gap of the Hall Effect sending unit, resulting in signal pulses. Some distributors employ one trigger wheel shutter/window for each engine cylinder; others use a single window to indicate cylinder No. 1 with additional sensors on the flywheel to indicate engine speed and TDC.

On models without timing/knock control units, vacuum and centrifugal advance mechanisms are used. Signals from the distributor Hall sending unit are sent back to the Hall control unit, which opens and closes the primary circuit to the ignition coil, firing the spark plugs.

On models utilizing a knock control unit, vacuum and centrifugal advance mechanisms are not used. The distributor Hall sending unit signal goes directly to the knock control unit which modifies the trigger signal to the ignition coil based on RPM, knock sensor input, and vacuum. On models with CIS-E models, throttle switch position signal is also used.