Preheat Circuit - Hitachi ZW180 Technical Manual

PREHEAT CIRCUIT (KEY SWITCH: ON)
•
When the key switch is turned to the ON position,
terminal B is connected to terminal M inside the
key switch.
•
Current from terminal M excites the battery relay
through fuse #8 of fuse box A. The battery power
is supplied to the intake-air heater relay through
the fuse (120A).
•
Current from fuse #7 of fuse box A flows to
terminal #39 of ECM.
•
ECM controls the exciting time of the intake-air
heater relay.
•
While the intake-air heater relay is excited, power
is supplied to the intake-air heater from the
intake-air heater relay and preheats it.
•
While preheating is made, as terminal #50 of
ECM is grounded, current flows from terminal
#1-24 of the monitor unit to terminal #50 of ECM.
Therefore, the monitor unit lights the preheat
indicator.
•
If preheating is not made, the preheat indicator
lights for two seconds in order to check the bulb
breakage of indicator.
SYSTEM / Electrical System
T2-4-6