320C Excavator Caterpillar

The Automatic Engine Speed Control (AEC) automatically reduces engine speed when the machine is inactive. The AEC system is designed to reduce fuel consumption and noise. Lower engine speeds can also increase engine life.

The AEC system will be inoperable while the backup switch of the electronic controller system is in the MAN position.

The engine rpm will recover automatically to the setting of the engine speed dial when any hydraulic function is activated. The AEC system operates in three modes. Refer to Table 1 for a description of each mode.

Illustration 1	g00682547
(1) Indicator for AEC mode (2) AEC switch

Automatic Engine Speed Control Switch (AEC Switch) - Automatic Engine Speed Control switch (2) and indicator (1) are activated when the engine start switch is turned to the ON position. When you press the AEC switch, the function of the AEC switch changes from ON to OFF, and vice versa. The operator can choose from three possible modes for automatic engine speed control. Refer to Table 1 for more details.

Illustration 2	g00735899
Manual low idle switch

The switch for manual low idle is on the right joystick.

Manual Low Idle - Activate the manual low idle in order to reduce the engine speed to approximately 950 rpm. Pressing the switch again will allow the engine speed to return to the original setting of the engine speed dial.

The manual low idle allows the operator to easily reduce the rpm without touching the engine speed dial. This is useful when the operator wants to reduce the engine speed in order to talk to someone or while the operator is waiting for a truck.

Operation of the automatic engine speed control depends on the position of the AEC switch and of the switch for manual low idle. The engine rpm will recover automatically to the setting of the engine speed dial when any hydraulic function is activated.

Table 1

AEC Mode	Position of AEC Switch	Setting of Engine Speed Dial	Position of Manual Low Idle Switch	Description of Mode
First stage	OFF	5 to 10	OFF	The electronic controller automatically reduces engine speed by 100 rpm after there has been no hydraulic demand for approximately three seconds.
Second stage	ON	5 to 10	OFF	The AEC system in the electronic controller will automatically reduce the engine rpm to approximately 1300 rpm after there has been no hydraulic demand for approximately three seconds.
Manual low Idle	ON or OFF	3 to 10	ON	The engine speed is reduced to approximately 950 rpm.