Doosan DX225LC, Manual, Page: 17 / 136

Electrical System SP000935
Page 16
ENGINE PREHEATING SYSTEM
An air heater (8) is installed in the intake manifold of the engine.
When the starter switch (5) is turned "ON," the current flows
from the battery (1)
o
fusible link (3)
o
fuse box (6)
o
"B"
terminal of starter switch (5)
o
"BR" terminal of starter switch (5)
o
"1-39" terminal of engine controller (12), causing current to
flow though "1-16" terminal of engine controller (12)
o
"C and
D" terminals of preheat relay (7)
o
"1-04" terminals of engine
controller (12)
o
ground.
This current flow causes the coil in preheat relay (7) to be
activated, closing contacts.
When the contacts of the preheat relay (7) are closed, the
heating coils of the air heating device (8) are heated by current
flowing from the battery (1)
o
battery relay (2)
o
preheat relay
(7)
o
air heater (8)
o
ground.
The duration of the heating cycle depends on the temperature of
engine coolant. The preheat indicator light in the instrument
panel (9) will turn "ON" during preheating cycle.
The preheat relay (7) is controlled by the engine controller (12)
and operates only at temperatures of 10°C (50°F) and below.
The longer the preheating period, the lower the temperature of
coolant is.