Heater Performance - Dodge 2000 DURANGO Service Manual

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DIAGNOSIS AND TESTING (Continued)
knob travel in each direction, with no spring-back of
the knob. If not OK, inspect the condition, routing,
installation and adjustment of the temperature con-
trol cable. See Temperature Control Cable in the
Removal and Installation section and in the Adjust-
ments section of this group for more information.
(2) Inspect and adjust the serpentine drive belt.
Refer to Group 7 - Cooling System for the procedures.
(3) Start the engine and hold the idle speed at
1,300 rpm.
(4) On vehicles with air conditioning, turn the
temperature control knob to the extreme counter-
clockwise (Cool) position, and set the mode control
switch knob in the Bi-Level (A/C) position. The out-
side (recirculation) air door should be open to outside
air. If not OK, see Vacuum System in the Diagnosis
and Testing section of this group.
(5) Open the vehicle windows. Test the blower
motor operation in all speeds. If not OK, see Blower
Motor in the Diagnosis and Testing section of this
group. Leave the blower motor switch knob in the
highest speed position.
(6) On vehicles with air conditioning, the compres-
sor should be running and the air conditioning sys-
tem in operation unless the ambient air temperature
is below about -1° C (30° F). If not OK, see A/C Per-
formance in the Diagnosis and Testing section of this
group.
(7) Check the mode control switch operation. The
heater and air conditioner systems should respond as
described in the owner's manual in the vehicle glove
box to each mode selected. Reduce the engine speed
Ambient Air Temperature
Minimum Heater System Air
Outlet Temperature
If the floor outlet air temperature is too low, refer
to Group 7 - Cooling System to check the engine cool-
ant temperature specifications. Both of the heater
hoses should be hot to the touch. The coolant return
heater hose should be slightly cooler than the coolant
supply heater hose. If the return hose is much cooler
than the supply hose, locate and repair the engine
coolant flow obstruction in the cooling system. Refer
to Group 7 - Cooling System for the procedures.
An alternate method of checking heater perfor-
mance is to use a DRB scan tool to monitor the
engine coolant temperature. The floor outlet air tem-
perature reading should be no more than 4.5° C (40°
F) lower than the engine coolant temperature read-
ing.
to normal idle. The vacuum will be high at low idle
and the vacuum actuators should respond quickly. If
not OK, see Vacuum System in the Diagnosis and
Testing section of this group.
(8) If the vacuum tests, and the electrical compo-
nent and circuit tests reveal no problems, disassem-
ble the heater-A/C housing to inspect for mechanical
misalignment or binding of the mode doors.

HEATER PERFORMANCE

Before performing the following tests, refer to
Group 7 - Cooling System for the procedures to check
the engine coolant level and flow, engine coolant
reserve/recovery system operation, accessory drive
belt condition and tension, radiator air flow and the
fan drive operation. Also be certain that the acces-
sory vacuum supply line is connected at the engine
vacuum source.
MAXIMUM HEATER OUTPUT
Engine coolant is delivered to the heater core
through two heater hoses. With the engine idling at
normal operating temperature, set the temperature
control knob in the full hot position, the mode control
switch knob in the floor position, and the blower
motor switch knob in the highest speed position.
Using a test thermometer, check the temperature of
the air being discharged at the heater-A/C housing
floor outlets. Compare the test thermometer reading
to the Temperature Reference chart.
Temperature Reference
15.5° C 21.1° C
(60° F) (70° F)
52.2° C 56.1° C
(126° F) (133° F)
OBSTRUCTED COOLANT FLOW
• Faulty water pump.
• Faulty thermostat.
• Pinched or kinked heater hoses.
• Improper heater hose routing.
• Plugged heater hoses or supply and return ports
at the cooling system connections.
• A plugged heater core.
If proper coolant flow through the cooling system is
verified, and heater outlet air temperature is still
low, a mechanical problem may exist.
MECHANICAL PROBLEMS
Possible locations or causes of insufficient heat:
• An obstructed cowl air intake.
• Obstructed heater system outlets.
HEATING AND AIR CONDITIONING
26.6° C
(80° F)
59.4° C
(139° F)
24 - 21
32.2° C
(90° F)
62.2° C
(144° F)