Dodge Durango (DN). Manual — part 191

• A faulty, obstructed or improperly installed

blend-air door.

• The temperature control cable is not connected,

or is not routed or adjusted properly.

• A faulty blower system.

• A faulty heater-A/C control.

TEMPERATURE CONTROL

If the heater outlet air temperature cannot be

adjusted with the temperature control knob on the

heater-A/C control panel, the following could require
service:

• A faulty heater-A/C control.

• The temperature control cable is not connected,

or is not routed or adjusted properly.

• A faulty, obstructed or improperly installed

blend-air door.

• An obstructed cowl air intake.

• The engine cooling system.

Heater Diagnosis

CONDITION

POSSIBLE CAUSE

CORRECTION

INSUFFICIENT HEATER
OUTPUT.

1. Incorrect engine
coolant level.
2. Air trapped in engine
cooling system.
3. Incorrect engine
coolant temperature.
4. Temperature control
cable improperly installed
or not adjusted.
5. Blend-air door not
operating properly.
6. Insufficient air flow
through heater housing.
7. Improper blower motor
operation.

1. Check the engine coolant level. Refer to Group 7 -
Cooling System for the procedures.
2. Check the operation of the coolant reserve/recovery
system. Refer to Group 7 - Cooling System for the
procedures.
3. Check the performance and operation of the engine
cooling system including: thermostat, water pump, fan
drive, accessory drive belt, coolant flow (plugged radiator
or heater core, plugged or kinked coolant hoses), air flow
(missing or improperly installed radiator air seals or fan
shroud). Refer to Group 7 - Cooling System for the
procedures.
4. See Temperature Control Cable in the Removal and
Installation and in the Adjustments sections of this group.
5. Check for a damaged, obstructed or improperly
installed blend-air door or seals. See Heater-A/C Housing
Door in the Removal and Installation section of this
group.
6. Remove foreign material or obstructions from cowl air
intake.
7. See Blower Motor in the Diagnosis and Testing section
of this group.

DUAL FUNCTION HIGH PRESSURE SWITCH/
HIGH PRESSURE CUT-OFF SWITCH

Before performing diagnosis of the dual function

high pressure switch, or the high pressure cut-off
switch, verify that the refrigerant system has the cor-
rect refrigerant charge. See Refrigerant System
Charge in the Service Procedures section of this
group for more information.

For circuit descriptions and diagrams, refer to

8W-42 - Air Conditioning/Heater in Group 8W - Wir-
ing Diagrams.

(1) Disconnect and isolate the battery negative

cable.

(2) Unplug the high pressure switch wire harness

connector from the switch on the refrigerant system
fitting.

(3) On the dual function high pressure switch,

check for continuity between terminals C and D. On

the

two

terminal

switch,

check

for

continuity

between both terminals of the high pressure cut-off
switch. There should be continuity. If OK, test and
repair the A/C switch sense circuit as required. If not
OK, replace the faulty switch.

LOW PRESSURE CUT-OFF SWITCH

Before performing diagnosis of the low pressure

cut-off switch, remember that lower ambient temper-
atures, below about -1° C (30° F), during cold
weather will open the switch contacts and prevent
compressor operation due to the pressure/tempera-
ture relationship of the refrigerant.

Also verify that the refrigerant system has the cor-

rect refrigerant charge. See Refrigerant System
Charge in the Service Procedures section of this
group for more information.

For circuit descriptions and diagrams, refer to Air

Conditioning/Heater in Wiring Diagrams.

24 - 22

HEATING AND AIR CONDITIONING

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DIAGNOSIS AND TESTING (Continued)

(1) Disconnect and isolate the battery negative

cable.

(2) Unplug the low pressure cut-off switch wire

harness connector from the switch on the suction line
jumper fitting.

(3) Install a jumper wire between the two cavities

of the low pressure cut-off switch wire harness con-
nector.

(4) Connect a manifold gauge set to the refrigerant

system service ports. See Refrigerant System Service
Equipment and Refrigerant System Service Ports in
the Description and Operation section of this group
for more information.

(5) Connect the battery negative cable.
(6) Place the heater-A/C mode control switch knob

in any A/C position and start the engine.

(7) Check for continuity between the two terminals

of the low pressure cut-off switch. There should be
continuity with a suction pressure (low side) reading
of 48 to 193 kPa (15 to 28 psi) or above, and no con-
tinuity with a suction pressure reading of 90 kPa (13
psi) or below. If OK, test and repair the A/C switch
sense circuit as required. If not OK, replace the
faulty switch.

REFRIGERANT SYSTEM LEAKS

WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE GENERAL INFORMATION SECTION
NEAR THE FRONT OF THIS GROUP BEFORE LEAK
TESTING THE SYSTEM.

If the air conditioning system does not cool prop-

erly, the A/C system performance should be tested.
See A/C Performance in the Diagnosis and Testing
section of this group for the procedures. If the A/C
system refrigerant fill is found to be low or if the sys-
tem is empty; a leak at a refrigerant line, connector
fitting, component, or component seal is likely.

An electronic leak detector designed for R-134a

refrigerant, or a fluorescent R-134a leak detection
dye and a black light are recommended for locating
and confirming refrigerant system leaks. Refer to the
operating instructions supplied by the equipment
manufacturer for the proper care and use of this
equipment.

An oily residue on or near refrigerant system lines,

connector fittings, components, or component seals
can indicate the general location of a possible refrig-
erant leak. However, the exact leak location should
be confirmed with an electronic leak detector prior to
component repair or replacement.

To detect a leak in the refrigerant system with an

electronic leak detector, perform one of the following
procedures:

SYSTEM EMPTY

(1) Evacuate the refrigerant system. See Refriger-

ant System Evacuate in the Service Procedures sec-
tion of this group.

(2) Connect and dispense 0.283 kilograms (0.625

pounds or 10 ounces) of R-134a refrigerant into the
evacuated refrigerant system. See Refrigerant Sys-
tem Charge in the Service Procedures section of this
group.

(3) Position the vehicle in a wind-free work area.

This will aid in detecting small leaks.

(4) With the engine not running, use an electronic

R-134a leak detector and search for leaks. Because
R-134a refrigerant is heavier than air, the leak detec-
tor probe should be moved slowly along the bottom
side of all refrigerant lines, connector fittings and
components.

CAUTION: Never insert a leak detector probe into
the outlet for the optional rear overhead A/C unit.
Failure to observe this caution could result in dam-
age to the rear blower wheel and/or the leak detec-
tor.

(5) To inspect the evaporator coil for leaks, insert

the electronic leak detector probe into the center
instrument panel outlet and the floor duct outlet, or
near the outside of the rear overhead A/C unit outlet
bezel. Set the front or rear blower motor switch to
the lowest speed position, and the mode control
switch to the recirculation mode (Max-A/C).

SYSTEM LOW

(1) Position the vehicle in a wind-free work area.

This will aid in detecting small leaks.

(2) Bring the refrigerant system up to operating

temperature and pressure. This is done by allowing
the engine to run with the air conditioning system
turned on for five minutes.

(3) With the engine not running, use an electronic

R-134a leak detector and search for leaks. Because
R-134a refrigerant is heavier than air, the leak detec-
tor probe should be moved slowly along the bottom
side of all refrigerant lines, connector fittings and
components.

CAUTION: Never insert a leak detector probe into
the outlet for the optional rear overhead A/C unit.
Failure to observe this caution could result in dam-
age to the rear blower wheel and/or the leak detec-
tor.

(4) To inspect the evaporator coil for leaks, insert

the electronic leak detector probe into the center
instrument panel outlet and the floor duct outlet, or
near the outside of the rear overhead A/C unit outlet
bezel. Set the front or rear blower motor switch to

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HEATING AND AIR CONDITIONING

24 - 23

DIAGNOSIS AND TESTING (Continued)

the lowest speed position, and the mode control
switch to the recirculation mode (Max-A/C).

REFRIGERANT SYSTEM SERVICE EQUIPMENT

WARNING: EYE PROTECTION MUST BE WORN
WHEN SERVICING AN AIR CONDITIONING REFRIG-
ERANT SYSTEM. TURN OFF (ROTATE CLOCKWISE)
ALL VALVES ON THE EQUIPMENT BEING USED,
BEFORE CONNECTING TO OR DISCONNECTING
FROM THE REFRIGERANT SYSTEM. FAILURE TO
OBSERVE THESE WARNINGS MAY RESULT IN PER-
SONAL INJURY.

When servicing the air conditioning system, a

R-134a refrigerant recovery/recycling/charging sta-
tion that meets SAE Standard J2210 must be used.
Contact an automotive service equipment supplier for
refrigerant

recovery/recycling/charging

equipment.

Refer to the operating instructions supplied by the
equipment manufacturer for the proper care and use
of this equipment.

A manifold gauge set may be needed with some

recovery/recycling/charging equipment (Fig. 9). The
service hoses on the gauge set being used should
have manual (turn wheel), or automatic back-flow
valves at the service port connector ends. This will
prevent refrigerant from being released into the
atmosphere.

MANIFOLD GAUGE SET CONNECTIONS

CAUTION: Do not use an R-12 manifold gauge set
on an R-134a system. The refrigerants are not com-
patible and system damage will result.

LOW PRESSURE GAUGE HOSE

The low pressure hose (Blue with Black stripe)

attaches to the suction service port. This port is
located on the compressor manifold, directly over the
suction port of the compressor.

HIGH PRESSURE GAUGE HOSE

The high pressure hose (Red with Black stripe)

attaches to the discharge service port. This port is
located on the liquid line between the condenser and
the evaporator, near the front of the engine compart-
ment.

RECOVERY/RECYCLING/EVACUATION/CHARGING HOSE

The center manifold hose (Yellow, or White, with

Black stripe) is used to recover, evacuate, and charge
the refrigerant system. When the low or high pres-
sure valves on the manifold gauge set are opened,
the refrigerant in the system will escape through this
hose.

VACUUM SYSTEM

Vacuum control is used to operate the mode doors

in the heater-A/C housing. Testing of the heater-A/C
mode control switch operation will determine if the
vacuum, electrical, and mechanical controls are func-
tioning. However, it is possible that a vacuum control
system that operates perfectly at engine idle (high
engine vacuum) may not function properly at high
engine speeds or loads (low engine vacuum). This can
be caused by leaks in the vacuum system, or by a
faulty or improperly installed vacuum check valve.

A vacuum system test will help to identify the

source of poor vacuum system performance or vac-
uum system leaks. Before starting this test, stop the
engine and make certain that the problem is not a
disconnected vacuum supply tube at the engine vac-
uum source or at the vacuum reservoir.

Use an adjustable vacuum test set (Special Tool

C-3707–B) and a suitable vacuum pump to test the
heater-A/C vacuum control system. With a finger
placed over the end of the vacuum test hose probe
(Fig. 10), adjust the bleed valve on the test set gauge
to obtain a vacuum of exactly 27 kPa (8 in. Hg.).
Release and block the end of the probe several times
to verify that the vacuum reading returns to the

Fig. 9 Manifold Gauge Set - Typical

1 – HIGH PRESSURE GAUGE
2 – VALVE
3 – VACUUM/REFRIGERANT HOSE (YELLOW W/BLACK

STRIPE)

4 – HIGH PRESSURE HOSE (RED W/BLACK STRIPE)
5 – LOW PRESSURE HOSE (BLUE W/BLACK STRIPE)
6 – VALVE
7 – LOW PRESSURE GAUGE

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HEATING AND AIR CONDITIONING

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DIAGNOSIS AND TESTING (Continued)

exact 27 kPa (8 in. Hg.) setting. Otherwise, a false
reading will be obtained during testing.

VACUUM CHECK VALVE

(1) Remove the vacuum check valve that is to be

tested. The valves are located in the vacuum supply
tube (black) at the power brake booster on the left
side of the engine compartment, and in the heater
and air conditioner vacuum take-out of the vacuum
supply tube in the engine compartment. The vacuum
check valve must be removed in order to perform the
following tests. See Vacuum Check Valve in the
Removal and Installation section of this group for the
procedures.

(2) Connect the test set vacuum supply hose to the

heater-A/C control side of the valve. When connected
to this side of the check valve, no vacuum should
pass and the test set gauge should return to the 27
kPa (8 in. Hg.) setting. If OK, go to step Step 3. If
not OK, replace the faulty valve.

(3) Connect the test set vacuum supply hose to the

engine vacuum side of the valve. When connected to
this side of the check valve, vacuum should flow
through the valve without restriction. If not OK,
replace the faulty valve.

HEATER-A/C CONTROLS

(1) Connect the test set vacuum probe to the heat-

er-A/C vacuum supply (black) tube in the engine
compartment. Position the test set gauge so that it
can be viewed from the passenger compartment.

(2) Place the heater-A/C mode control switch knob

in each mode position, one position at a time, and
pause after each selection. The test set gauge should

return to the 27 kPa (8 in. Hg.) setting shortly after
each selection is made. If not OK, a component or
vacuum line in the vacuum circuit of the selected
mode has a leak. See Locating Vacuum Leaks in the
Diagnosis and Testing section of this group.

CAUTION: Do not use lubricant on the switch ports
or in the holes in the plug, as lubricant will ruin the
vacuum valve in the switch. A drop of clean water
in the connector plug holes will help the connector
slide onto the switch ports.

LOCATING VACUUM LEAKS

WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS,

REFER

TO

GROUP

8M

-

PASSIVE

RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING

WHEEL,

STEERING

COLUMN,

OR

INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.

(1) Disconnect the vacuum harness connector from

the back of the heater-A/C mode control switch on
the instrument panel.

(2) Connect the test set vacuum hose probe to each

port in the vacuum harness connector, one port at a
time, and pause after each connection (Fig. 11). The
test set gauge should return to the 27 kPa (8 in. Hg.)
setting shortly after each connection is made. If OK,
replace the faulty heater-A/C control. If not OK, go to
Step 3.

Fig. 10 Adjust Vacuum Test Bleed Valve

1 – VACUUM PUMP TOOL C-4289
2 – VACUUM TEST SET C-3707
3 – BLEED VALVE
4 – PROBE

Fig. 11 Vacuum Circuit Test

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HEATING AND AIR CONDITIONING

24 - 25

DIAGNOSIS AND TESTING (Continued)