equipped with a supplemental cabin heater. This
cabin heater is mounted under the vehicle and oper-
ates 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 cabin heater and then to the front
heater core. This provides additional heat to the pas-
senger compartment. The supplemental cabin heater
system is interfaced to the vehicles on-board com-
puter systems and DRBIII

t diagnostics.

The supplemental cabin heater has an electronic

control module that monitors the heat output of the
heater. The cabin heater operates at full load (5 kW),
half load or idle mode (no additional heat) depending
on engine coolant temperature.

OPERATION

The supplemental cabin heater is activated by

using the temperature control on the A/C-heater con-
trol. The supplemental cabin heater is activated
when the temperature control is set to/or above the
upper set point. The supplemental cabin heater can
operate in a full or partial load range as well as an
idle mode, all dependent on the engine coolant tem-
perature. The heater unit will also turn off if the
temperature control is set to less than the lower set
point. The supplemental cabin 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 cabin heater only operates when

the engine is running, the mileage exceeds 8 kilome-
ter (5 mph) and the fuel tank volume exceeds 1/8 of a
tank. The heater should start if the coolant temper-
ature is below 40° C (104° F).

NOTE: Do not apply a strong vacuum directly on
the supplemental cabin heater exhaust line. Place
the vacuum 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 blower speed and combustion during its start-
up.

DIAGNOSIS AND TESTING

SUPPLEMENTAL CABIN HEATER

Refer to the Symptoms Diagnosis table for basic

checks of the diesel fueled supplemental cabin heater.

24 - 104

CABIN HEATER

SYMPTOMS DIAGNOSIS

Symptom

Possible Causes

Smell of diesel fuel.

Check cabin heater system integration in vehicle’s fuel system. Check
fuel lines for leakage, kinks or obstructions. If OK, Inspect the inlet
muffler, drain as necessary. Re-test the cabin heater and re-inspect.
Inspect the exhaust tube and cabin heater for the presence of exter-
nal fuel. If presence of external fuel is observed on the heater unit or
in the exhaust tube or after draining and testing. Remove the cabin
heater from vehicle and repair or replace components as required.

Heater does not achieve full load op-
eration.

Check cabin heater operation with DRBIII

scan tool and replace

components as required.

Continuous white smoke from heater
exhaust during combustion operation.

Check cabin heater operation with DRBIII

scan tool and replace

components as required. White smoke is typical in extreme weather
conditions.

Heater can not be switched off.

Check cabin heater operation with DRBIII

scan tool and replace

components as required.

Heater does not operate.

Diagnosis cabin heater control module using the DRBIII

scan tool

and the procedures listed in Vehicle Performance under Cabin Heater
Diagnosis in Group 18.

Loss of coolant (Leakage) or heater
develops smoke during combustion
operation and exhaust has an ex-
tremely sweet smell.

Inspect coolant hoses for leakage, kinks or loose hose connection.
Inspect the exhaust tube assembly for continuous flow, if OK there is
an internal heater leak and cabin heater should be inspected and
components should be replaced as required.

Loss of fuel (dripping).

Check cabin heater system integration in vehicles fuel system. Check
fuel line connection for leakage. If OK there is an internal leak and
cabin heater should be inspected and replaced as required.

EXHAUST TUBE

REMOVAL

WARNING: There is a potential danger of skin burns
as the supplemental cabin heater unit and its com-
ponents can become very hot. Make sure the heater
unit is allowed to cool down before any service
work on the cabin heater system is attempted. Fail-
ure to observe this warning may result in possible
personal injury.

(1) Raise and support the vehicle while taking note

of the location of the flexible exhaust tube section.

(2) Remove the exhaust clamp at the flexible pipe

and steel pipe connection (Fig. 1).

CABIN HEATER

24 - 105

(3) Remove the clamp at the flexible pipe connec-

tion

and

the

supplemental

heater

housing

(if

required).

(4) Remove the three screws holding the exhaust

pipe to the body.

(5) Remove the steel exhaust pipe from the vehi-

cle.

(6) Remove the flexible exhaust pipe from the

vehicle (if required).

INSTALLATION

(1) Install the flexible exhaust pipe to the heater

unit. Tighten mounting clamp securely.

(2) Position the steel exhaust pipe to the flexible

exhaust and install and tighten the mounting clamp
securely.

(3) Install the three exhaust pipe screws, adjust

pipe placement as needed and tighten the screws
securely.

(4) Install the clamp to connect the steel exhaust

pipe to the flexible exhaust pipe and tighten clamp
securely.

(5) Check exhaust pipe exhaust end placement and

make any final adjustments.

(6) Lower the vehicle.

FUEL DOSING PUMP

DESCRIPTION

The dosing pump is a combined delivery, dosing

and shut-off system for the fuel supply to the supple-
mental cabin heater from the vehicle fuel tank.

OPERATION

The dosing pump is an electrically operated pump

that receives its operation instructions from the sup-
plemental cabin heater control module. The pump
supplies diesel fuel from the vehicle fuel tank to the
cabin heater.

REMOVAL

NOTE: The dosing pump is serviceable without
removing the component from the vehicle.

(1) Disconnect the rubber hose at the fuel line to

heater fuel pump. Leave the rubber hose on the fuel
line (Refer to 24 - HEATING & AIR CONDITION-
ING/CABIN HEATER/FUEL LINE - REMOVAL)
(Fig. 2).

(2) Disconnect the fuel line between the dosing

pump and the cabin heater unit.

Fig. 1 Cabin Heater Exhaust System

1 - MOUNTING SCREW (3)
2 - STEEL HEATER EXHAUST PIPE
3 - EXHAUST CLAMP (2)

4 - FLEXIBLE HEATER EXHAUST PIPE
5 - HEATER SHIELD
6 - EXHAUST PIPE MOUNTING CLIP (3)

24 - 106

CABIN HEATER

NOTE: Position and retain the heater fuel line to
prevent fuel leakage while servicing the dosing
pump.

NOTE: Utilize an approved fuel storage container to
catch any residual fuel.

(3) Disconnect the wiring harness connector to the

fuel pump by depressing the integral spring and pull-
ing the connector away from the pump.

(4) Remove the dosing pump from the rubber iso-

lator.

INSTALLATION

(1) Install the dosing pump onto the rubber isola-

tor.

(2) Connect the fuel lines to the dosing pump and

the cabin heater unit.

NOTE: The connectors should point towards the
cabin heater fuel line.

(3) Use aviation style clamps to attach the hose to

the fuel pump nipples (Refer to 24 - HEATING &
AIR CONDITIONING/CABIN HEATER/FUEL LINE
- INSTALLATION).

(4) Connect the wire harness connector to the fuel

pump by depressing the integral spring and pushing

the connector towards the dosing pump. Pull the con-
nector towards the cabin heater to verify the instal-
lation.

(5) Verify

function

the

supplemental

cabin

heater.

FUEL LINE

STANDARD PROCEDURE

CLEANING

(1) Remove the cabin heater fuel line (Refer to 24 -

HEATING & AIR CONDITIONING/CABIN HEAT-
ER/FUEL LINE - REMOVAL).

(2) With the cabin heater fuel line removed from

the vehicle, place a shop cloth on the fuel tank end of
the fuel line to catch any residue, then apply a small
amount of air pressure to the other end of the fuel
line.

(3) Check to see if air pressure is coming from the

tank end of the line. If pressure is flowing unre-
stricted the line is clean.

(4) If the fuel line shows any signs of being

restricted after air pressure is applied, the fuel line
should be replaced.

Fig. 2 Cabin Heater Dosing Pump Fuel Line

1 - FUEL LINE
2 - RETAINING CLAMP

3 - DOSING PUMP
4 - HEATER AIR INTAKE PIPE

CABIN HEATER

24 - 107

Content .. 355 356 357 358 ..