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GENERAL INFORMATION
CAUTION: Do not actuate the DCHA Field
Mode Test with the engine off. Failure to
follow these instructions may result in
internal damage to the DCHA Heater Module.
CAUTION: Always Perform The Cabin Heater
Pre-Test Prior To Performing Any Other Cabin
Heater Test For The Test Result To Be Valid.
NOTE: Do not disconnect the vehicle's
battery or the DCHA's main power-supply
while the DCHA is in operation or in
run-down mode. Failure to follow these
instructions may result in excess emissions
from the DCHA Heater Module.
NOTE: Failure to prime the Dosing Pump
after draining the DCHA fuel line will prevent
DCHA heater activation during the first
attempt to start the heater. This will also set a
Diagnostic Trouble Code (DTC) in the DCHA
Control's memory. Do not perform the Dosing
Pump Priming Procedure if an attempt was
made to start the DCHA without priming the
Dosing Pump first. This will put excess fuel
in the DCHA Heater Module and cause smoke
to emit from the DCHA exhaust pipe when
heater activation occurs.
NOTE: Waxed fuel can obstruct the fuel line
and reduce flow. Check for the appropriate
winter grade fuel and replace as necessary.
3.10.2 COMPONENT DESCRIPTION AND
OPERATION
3.10.2.1 DCHA ASSEMBLY
The DCHA is a supplemental heater designed to
pre-heat the engine's coolant in order to supply the
vehicle's occupants with heat prior to the engine
reaching operating temperature. The DCHA assem-
bly mounts underneath the vehicle on the left side
floor pan near the front door opening. The DCHA
assembly connects to the vehicle's heater hoses and
has a fuel supply line that connects to the vehicle's
fuel tank.
The DCHA assembly consists of a:
•
combustion air fan assembly
•
burner housing
•
burner insert
•
control unit/heat exchanger
•
combustion chamber
•
dosing pump
3.10.2.2 COMBUSTION AIR FAN
The combustion air fan assembly includes the:
•
combustion air fan
•
combustion air fan inlet
•
fuel supply inlet
The combustion air fan delivers the air required
for combustion from the combustion air inlet to the
burner insert.
3.10.2.3 BURNER HOUSING
The burner housing includes the:
•
coolant inlet
•
coolant outlet
•
exhaust outlet
The burner housing accommodates the burner
insert and is combined with the control unit/heat
exchanger as an assembly.
3.10.2.4 BURNER INSERT
The burner insert includes the:
•
combustion pipe fuel cross section
•
glow plug/flame sensor
Inside the burner insert, fuel is distributed across
the combustion-pipe fuel cross section. Combustion
of the fuel/air mixture takes place within the com-
bustion pipe to heat the exchanger. The glow plug/
flame sensor, located in the burner insert, ignites
the fuel/air mixture during heater start up. After
heater start up, the glow plug/flame sensor operates
in the flame sensor function. The glow plug/flame
sensor is an electrical resistor by design, and is
located in the burner insert opposite the flame side.
3.10.2.5 CONTROL UNIT/HEAT
EXCHANGER
The control unit/heat exchanger includes the:
•
control unit
•
temperature sensor
•
overheat protection
•
heat exchanger
•
connector terminal
The control unit controls and monitors combus-
tion operation. The control unit is ventilated by
means of a ventilation hose routed from the com-
bustion air collector compartment of the burner.
The heat exchanger transfers the heat generated by
combustion to the coolant circuit. The control unit/
heat exchanger and the burner housing are an
assembly and must not be disassembled.
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