Control Unit

The electronic control unit, located in a metal housing on the firewall, receives the voltage pulses or signals from the distributor. This causes the transistor to interrupt current flow to the ignition coil primary circuit. This break in the primary circuit causes a high voltage surge in the secondary circuit, firing the spark plugs. One plug fires each time a reluctor tooth passes the magnetic pick-up coil's pole piece.

The control unit functions whenever the ignition is switched to "START" or "ON". It allows current to flow through the primary side of the coil, creating a magnetic field in the coil. The length of time current flows through the primary (dwell) is determined by the control unit and is not adjustable.