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Ford Smart Charge High Output Alternators Explained

Ford Smart Charge was introduced on the 1999 Windstar. Like the GM system, the regulator is mounted in the alternator. The PCM then controls the regulator to control system output. It’s similar to the operation of the GM system, with two main control connections to the alternator: generator monitor (GEN MON) and generator command (GEN COM). GEN MON and GEN COM are similar to terminals F and L on a GM system (figure 2).

GEN COM — Generator command controls the system output. The PCM sends a 128 HZ PWM signal to the alternator GEN COM terminal. The duty cycle varies from 3% to 95% with the high duty cycle corresponding to higher alternator output.

If the battery voltage is correct, there won’t be a signal on the GEN COM circuit. If an open circuit occurs, the output voltage default will be 13.5- 13.7 volts after engine speed exceeds 2500 RPM the first time.

GEN MON — Generator monitor sends a signal to the PCM based on the alternator load and output. The PCM sends a signal to the alternator GEN MON circuit. The regulator then grounds or ungrounds the circuit at a fixed frequency (generally 128Hz), but varies the duty cycle from 5-95% based on the alternator load. The GEN MON circuit will have a signal present anytime the engine is operating.

SENSE — the alternator receives the current battery voltage from the sense circuit.

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