Hitachi ZW180 Technical Manual page 112

Overheat Indicator Control
Purpose: To light the overheat indicator on monitor unit
in order to inform the abnormal rising in the
engine coolant temperature to the operator.
Operation:
1. When the engine coolant temperature exceeds
the normal value, ECM excites the overheat relay.
Therefore, terminal 1-7 of the monitor unit is
grounded.
2. When terminal 1-7 of the monitor unit is grounded,
the monitor unit lights the overheat indicator.
Overheat Indicator
Stop Indicator
SYSTEM / ECM System
From Fuse #9 of
Fuse Box B
Diode G
Monitor
Unit
1-7
3. When the engine coolant temperature returns to
the normal value, ECM demagnetizes the
overheat relay. Therefore, terminal 1-7 of the
monitor unit is disconnected from the ground.
4. When terminal 1-7 of the monitor unit is
disconnected from the ground, the monitor unit
turns off the overheat indicator.
NOTE: The monitor unit lights the stop indicator as
well as the overheat indicator.
Overheat Relay
T2-2-6
ECM
49
T4GD-02-02-005