40 AB Volvo Penta / Diesel Engine TAMD71B
9.6 GAC Speed Control Unit
The task of the GAC unit is to control engine
speed to maintain a set speed (1500 or 1800
rpm). A tacho sender provides a sine-wave sig-
nal to the GAC unit, with a frequency proportion-
al to engine speed. Please refer to
Function –
Installation, Electronic Speed Governor
for oper-
ation of the GAC unit.
Fig. 9.8 GAC Speed Control Unit
The tacho sender value is compared with the pre-set value,
speed. The difference is used to control the fuel injection of the
engine, to maintain correct engine speed.
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