CABIN HEATER
TABLE OF CONTENTS
page page
CABIN HEATER
DESCRIPTION .........................72
OPERATION ...........................72
DIAGNOSIS AND TESTING - DIESEL
SUPPLEMENTAL HEATER - DCHA ........72
EXHAUST TUBE
REMOVAL .............................73
INSTALLATION .........................73
FUEL DOSING PUMP
DESCRIPTION .........................74
OPERATION ...........................74
REMOVAL .............................74
INSTALLATION .........................74
FUEL LINE
STANDARD PROCEDURE - CLEANING ......75
REMOVAL .............................75
INSTALLATION .........................76
HEATER UNIT
REMOVAL
REMOVAL ...........................77
REMOVAL ...........................77
INSTALLATION
INSTALLATION .......................78
INSTALLATION .......................78
INLET HOSE
REMOVAL .............................78
INSTALLATION .........................78
CABIN HEATER
DESCRIPTION
Vehicles equipped with the optional diesel engine
are also equipped with a supplemental heater unit.
This unit is mounted under the vehicle and operates
similar to an oil fired furnace. The heater burns
small amounts of fuel to provide additional heat to
the coolant. Coolant is routed from the engine, to the
supplemental heater, and then to the front heater
core. This provides additional heat to the passenger
compartment. The system is interfaced to the vehi-
cles on-board computer systems and DRBIIIt diag-
nostics.
The supplemental heater unit has an electronic
control module that monitors the heat output of the
heater. The heater operates at full load (5 kW), half
load or idle mode (no additional heat) depending on
coolant temperature.
OPERATION
The supplemental heater is activated via the tem-
perature control on the heater-A/C control. The
heater is activated when the temperature control is
set to/or above the upper set point. The supplemental
heater can operate in a full or partial load range as
well as an idle mode, all dependent on the engine
coolant temperature. The heater unit will also turn
off if the temperature control is set to less than the
lower set point. The supplemental heater can take up
to three minutes to completely shut down when
either the heater temperature is set below the lower
set point or the vehicle ignition is turned off.
The supplemental heater only operates when the
engine is running, the mileage exceeds 8 kilometer (5
mph) and the fuel tank volume exceeds 1/8 of a tank.
The heater should start if the coolant temperature is
below 40° C (104° F).
NOTE: Do not apply a strong vacuum directly on
the supplemental heater exhaust line. Place the vac-
uum within 75 mm (3 inches) of the exhaust port.
Too strong of a vacuum can prevent the heater from
starting. The heater control module monitors the
supplemental blower speed and combustion during
its start-up.
DIAGNOSIS AND TESTING - DIESEL
SUPPLEMENTAL HEATER - DCHA
Refer to the Symptoms Diagnosis table for basic
checks of the diesel fueled supplemental heater.
24 - 72 CABIN HEATER VA
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