Generator, description of operation
When the engine starts, the engine control module (ECM) sends a signal to the generator connection L. The generator connection L is coupled to the magnetization winding, which means that the generator begins to charge. To maintain the charge, the engine control module continuously sends out a signal to connection L.
When the rotor in the generator rotates, the magnetic field around the rotor will also rotate and thereby generate an AC voltage in the stator winding. This AC voltage is rectified when it passes the diodes and is then supplied to the car's electrical system via B+. The voltage obtained from the stator winding also passes to the voltage regulator and affects its regulating function. When the voltage exceeds the nominal value (approx. 14V), the voltage regulator will reduce the current through the magnetization winding. The magnitude of the magnetic field will be reduced, as will the AC voltage generated in the stator winding. When the voltage has dropped below the nominal value, the magnetization current will increase again, the magnetic field will increase and thereby the charge.
If the engine idle speed falls below the programmed speed, the signal from the engine control module to the connection L is broken. This means that the generator does not receive any magnetization and does not charge. The engine load is reduced and the risk of stalling avoided.
Connection L is also the diagnostic lead from the generator to the engine control module. If the generator does not charge, an indicator will be displayed on SID and the engine control module will generate a diagnostic trouble code.
Connection F on the generator in cars with petrol engine informs the engine control module of the generator load, i.e. how much it is charging, so that the engine control module can correct the engine torque to avoid the engine speed changing as the generator load changes. Connection F on the generator is not used in cars with diesel engines.