Principles of Operation: Functionality

With the key in the ON position (dual generator system), voltage is supplied by the PCM controlled I circuit 1183 (WH/YE) to I circuit 904 (LG/RD) to the upper generator and through the I circuit 1185 (YE) from the PCM to the I circuit 1183 (WH/YE) at the lower generator. If the glow plug system is not cycling, the PCM maintains voltage to the lower generator. If the glow plug system is cycling, the PCM supplies voltage to the lower generator momentarily to verify there is a volt drop, then shuts off the voltage on the lower generator I circuit 1185 (YE)/1183 (WH/YE). Once the glow plug system stops cycling, the PCM supplies voltage on the lower generator I circuit 1185 (YE)/1183 (WH/YE), which turns the voltage regulator on allowing current to flow from the battery sense A circuit to the generator field coil, at which time it begins to function normally. The PCM maintains voltage on the upper generator I circuit 1183 (WH/YE)/904 (LG/RD), which turns on the voltage regulator, allowing current to flow from the battery sense A circuit to the generator field coil.

Once the generator begins generating current, a voltage signal is taken from the generator stator and fed back to the voltage regulator internally. This voltage feedback signal (typically one-half of the battery voltage) is used by the PCM to turn off the charging system warning indicator.

With the system functioning normally, the generator output current is determined by the voltage of the A circuit 35 (OG/LB). The A circuit 35 (OG/LB) voltage is compared to a set voltage internal to the voltage regulator, and the voltage regulator controls the generator field current to maintain the correct generator output.

The set voltage varies with temperature and is typically higher in cold temperatures and lower in warm temperatures. This allows for more efficient battery recharge in the winter and reduces the chance of overcharging in the summer.