Dodge Durango (DN). Manual — part 188

refrigerant hoses are made from lightweight alumi-
num or steel, and commonly use braze-less fittings.

Any kinks or sharp bends in the refrigerant plumb-

ing will reduce the capacity of the entire air condi-
tioning system. Kinks and sharp bends reduce the
flow of refrigerant in the system. A good rule for the
flexible hose refrigerant lines is to keep the radius of
all bends at least ten times the diameter of the hose.
In addition, the flexible hose refrigerant lines should
be routed so they are at least 80 millimeters (3
inches) from the exhaust manifold.

OPERATION

High pressures are produced in the refrigerant sys-

tem when the air conditioning compressor is operat-
ing. Extreme care must be exercised to make sure
that each of the refrigerant system connections is
pressure-tight and leak free. It is a good practice to
inspect all flexible hose refrigerant lines at least once
a year to make sure they are in good condition and
properly routed.

The refrigerant lines and hoses are coupled with

other components of the HVAC system with peanut-
block style fittings. A stat-O seal type flat steel gas-
ket with a captured compressible O-ring, and spring
lock coupler, is used to mate plumbing lines with A/C
components to ensure the integrity of the refrigerant
system.

The refrigerant lines and hoses cannot be repaired

and, if faulty or damaged, they must be replaced.

REFRIGERANT LINE COUPLERS

DESCRIPTION

Spring-lock type refrigerant line couplers are used

to connect many of the refrigerant lines and other
components to the refrigerant system. These couplers
require a special tool for disengaging the two coupler
halves.

OPERATION

The spring-lock coupler is held together by a garter

spring inside a circular cage on the male half of the
fitting (Fig. 5). When the two coupler halves are con-
nected, the flared end of the female fitting slips
behind the garter spring inside the cage on the male
fitting. The garter spring and cage prevent the flared
end of the female fitting from pulling out of the cage.

Two O-rings on the male half of the fitting are

used to seal the connection. These O-rings are com-
patible with R-134a refrigerant and must be replaced
with O-rings made of the same material.

Secondary clips are installed over the two con-

nected coupler halves at the factory for added blowoff
protection.

REFRIGERANT OIL

DESCRIPTION

The refrigerant oil used in R-134a refrigerant sys-

tems is a synthetic-based, PolyAlkylene Glycol (PAG),
wax-free lubricant. Mineral-based R-12 refrigerant
oils are not compatible with PAG oils, and should
never be introduced to an R-134a refrigerant system.

There are different PAG oils available, and each

contains a different additive package. The SD7H15
compressor used in this vehicle is designed to use an
SP-20 PAG refrigerant oil. Use only refrigerant oil of
this same type to service the refrigerant system.

OPERATION

After performing any refrigerant recovery or recy-

cling operation, always replenish the refrigerant sys-
tem with the same amount of the recommended
refrigerant oil as was removed. Too little refrigerant
oil can cause compressor damage, and too much can
reduce air conditioning system performance.

PAG refrigerant oil is much more hygroscopic than

mineral oil, and will absorb any moisture it comes
into contact with, even moisture in the air. The PAG
oil container should always be kept tightly capped
until it is ready to be used. After use, recap the oil
container immediately to prevent moisture contami-
nation.

Fig. 5 Spring-Lock Coupler - Typical

1 – MALE HALF SPRING-LOCK COUPLER
2 – FEMALE HALF SPRING-LOCK COUPLER
3 – SECONDARY CLIP
4 – CONNECTION INDICATOR RING
5 – COUPLER CAGE
6 – GARTER SPRING
7 – COUPLER CAGE
8 – “O” RINGS

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HEATING AND AIR CONDITIONING

DN

DESCRIPTION AND OPERATION (Continued)

REFRIGERANT SYSTEM SERVICE PORTS

DESCRIPTION

The two refrigerant system service ports are used

to charge, recover/recycle, evacuate, and test the air
conditioning refrigerant system. Unique service port
coupler sizes are used on the R-134a system, to
ensure that the refrigerant system is not accidentally
contaminated by the use of the wrong refrigerant
(R-12), or refrigerant system service equipment.

OPERATION

The high pressure service port is located on the liq-

uid line between the condenser and the evaporator,
near the front of the engine compartment. The low
pressure service port is located on the compressor
manifold, directly over the suction port of the com-
pressor.

Each of the service ports has a threaded plastic

protective cap installed over it from the factory. After
servicing the refrigerant system, always reinstall
both of the service port caps.

VACUUM CHECK VALVE

DESCRIPTION

Two vacuum check valves are installed in the

accessory vacuum supply line in the engine compart-
ment. One check valve is located near the vacuum
fitting on the power brake booster. The second check
valve is located at the heater and air conditioner
take-out of the accessory vacuum supply line. The
vacuum check valves are designed to allow vacuum
to flow in only one direction through the accessory
vacuum supply circuits.

OPERATION

The use of the vacuum check valves help to main-

tain the system vacuum needed to retain the selected
heater-A/C mode settings. The check valves will pre-
vent the engine from bleeding down system vacuum
through the intake manifold during extended heavy
engine load (low engine vacuum) operation.

The vacuum check valves cannot be repaired and,

if faulty or damaged, they must be individually
replaced.

VACUUM RESERVOIR

DESCRIPTION

The vacuum reservoir is mounted to the underside

of the cowl plenum cover/grille panel in the right
cowl plenum area. The cowl plenum cover/grille panel
must be removed from the vehicle to access the vac-
uum reservoir for service.

OPERATION

Engine vacuum is stored in the vacuum reservoir.

The stored vacuum is used to operate the vacuum-
controlled vehicle accessories during periods of low
engine vacuum such as when the vehicle is climbing
a steep grade, or under other high engine load oper-
ating conditions.

The vacuum reservoir cannot be repaired and, if

faulty or damaged, it must be replaced.

DIAGNOSIS AND TESTING

A/C PERFORMANCE

The air conditioning system is designed to provide

the passenger compartment with low temperature
and low humidity air. The evaporators, located in the
heater-A/C housing on the dash panel below the
instrument panel and in the rear overhead A/C unit
housing above the headliner, are cooled to tempera-
tures near the freezing point. As warm damp air
passes through the cooled evaporators, the air trans-
fers its heat to the refrigerant in the evaporator
tubes and the moisture in the air condenses on the
evaporator fins. During periods of high heat and
humidity, an air conditioning system will be more
effective in the recirculation mode (Max-A/C). With
the system in the recirculation mode, only air from
the passenger compartment passes through the evap-
orator. As the passenger compartment air dehumidi-
fies, the air conditioning system performance levels
improve.

Humidity has an important bearing on the temper-

ature of the air delivered to the interior of the vehi-
cle. It is important to understand the effect that
humidity has on the performance of the air condition-
ing system. When humidity is high, the evaporator
has to perform a double duty. It must lower the air
temperature, and it must lower the temperature of
the moisture in the air that condenses on the evapo-
rator fins. Condensing the moisture in the air trans-
fers heat energy into the evaporator fins and tubing.
This reduces the amount of heat the evaporator can
absorb from the air. High humidity greatly reduces
the ability of the evaporator to lower the temperature
of the air.

However, evaporator capacity used to reduce the

amount of moisture in the air is not wasted. Wring-
ing some of the moisture out of the air entering the
vehicle adds to the comfort of the passengers.
Although, an owner may expect too much from their
air conditioning system on humid days. A perfor-
mance test is the best way to determine whether the
system is performing up to standard. This test also
provides valuable clues as to the possible cause of
trouble with the air conditioning system.

DN

HEATING AND AIR CONDITIONING

24 - 11

DESCRIPTION AND OPERATION (Continued)

Review the Service Warnings and Precautions in

the General Information section near the front of this
group before performing this procedure. The air tem-
perature in the test room and in the vehicle must be
a minimum of 21° C (70° F) for this test.

(1) Connect a tachometer and a manifold gauge

set.

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

the recirculation mode (Max-A/C) position, the tem-
perature control knob in the full cool position, and
the blower motor switch knob in the highest speed
position.

(3) Start the engine and hold the idle at 1,000 rpm

with the compressor clutch engaged. If the compres-
sor clutch does not engage, see the A/C Diagnosis
chart in the Diagnosis and Testing section of this
group.

(4) The engine should be at operating temperature.

The doors and windows must be closed and the hood
must be mostly closed.

CAUTION: Never insert a thermometer 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 thermome-
ter.

(5) Insert a thermometer in the driver side center

A/C (panel) outlet for testing of the front unit, or
hold a thermometer near the center outlets in the

headliner for testing of the rear unit. Operate the
engine for five minutes.

(6) With the compressor clutch engaged, record the

panel outlet or left center outlet discharge air tem-
perature, the condenser out pressure (high side), and
the compressor inlet pressure (low side). The com-
pressor clutch may cycle, depending upon the ambi-
ent temperature and humidity. If the clutch cycles,
use the readings obtained before the clutch disen-
gaged.

(7) Compare the discharge air temperature read-

ing to the Performance Temperature and Pressure
chart. If the temperature reading is high for the rear
unit, see Refrigerant System Leaks in the Diagnosis
and Testing section of this group, and Refrigerant
System Charge in the Service Procedures section of
this group. If the temperature reading is high for the
front unit, clamp off both heater hoses (inlet and out-
let), wait five minutes and record the temperature
again. Compare the second reading to the Perfor-
mance Temperature and Pressure chart. If the tem-
perature

reading

is

now

OK,

see

Temperature

Control Cable in the Removal and Installation sec-
tion and in the Adjustments section of this group. If
the temperature reading is still too high, see Refrig-
erant System Leaks in the Diagnosis and Testing sec-
tion of this group, and Refrigerant System Charge in
the Service Procedures section of this group.

Performance Temperature and Pressure

Ambient Temperature

21°C

(70°F)

27°C

(80°F)

32°C

(90°F)

38°C

(100°F)

43°C

(110°F)

Maximum Allowable Air

Temperature at Left Center

Panel Outlet

9°C

(48°F)

9°C

(48°F)

12°C

(54°F)

15°C

(59°F)

18°C

(65°F)

Compressor Inlet Pressure

(Low Side)

138 to 207

kPa

(20 to 30 psi)

138 to 207

kPa

(20 to 30 psi)

172 to 241

kPa

(25 to 35 psi)

214 to 283

kPa

(31 to 41 psi)

255 to 324

kPa

(37 to 47 psi)

Condenser Out Pressure at

Service Port (High Side)

689 to 1034

kPa

(100 to 150

psi)

931 to 1276

kPa

(135 to 185

psi)

1172 to 1517

kPa

(170 to 220

psi)

1448 to 1758

kPa

(210 to 255

psi)

1689 to 2034

kPa

(245 to 295

psi)

(8) Compare the discharge (high side) and suction

(low side) pressure readings to the Performance Tem-
perature and Pressure chart. If the pressures are

abnormal, suction pressure is not normal, see the A/C
Diagnosis chart in the Diagnosis and Testing section
of this group.

24 - 12

HEATING AND AIR CONDITIONING

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DIAGNOSIS AND TESTING (Continued)

A/C Diagnosis

CONDITION

POSSIBLE CAUSE

CORRECTION

RAPID COMPRESSOR
CLUTCH CYCLING (TEN
OR MORE CYCLES PER
MINUTE).

1. Low refrigerant system
charge.
2. Faulty electronic
cycling clutch switch.
3. Faulty Powertrain
Control Module (PCM).

1. See Refrigerant System Leaks in the Diagnosis and
Testing section of this group. Test the refrigerant system
for leaks. Repair, evacuate and charge the refrigerant
system, if required.
2. See Electronic Cycling Clutch Switch in the Diagnosis
and Testing section of this group. Test the electronic
cycling clutch switch and replace, if required.
3. Refer to the proper Diagnostic Procedures manual for
testing of the PCM. Test the PCM and replace, if
required.

EQUAL PRESSURES,
BUT THE
COMPRESSOR CLUTCH
DOES NOT ENGAGE.

1. No refrigerant in the
refrigerant system.
2. Faulty fuse.
3. Faulty compressor
clutch coil.
4. Faulty compressor
clutch relay.
5. Faulty electronic
cycling clutch switch.
6. Faulty low pressure
cut-off switch.
7. Faulty high pressure
cut-off switch.
8. Faulty Powertrain
Control Module (PCM).
9. Faulty heater-A/C
control.

1. See Refrigerant System Leaks in the Diagnosis and
Testing section of this group. Test the refrigerant system
for leaks. Repair, evacuate and charge the refrigerant
system, if required.
2. Check the fuses in the Power Distribution Center and
the junction block. Repair the shorted circuit or
component and replace the fuses, if required.
3. See Compressor Clutch Coil in the Diagnosis and
Testing section of this group. Test the compressor clutch
coil and replace, if required.
4. See Compressor Clutch Relay in the Diagnosis and
Testing section of this group. Test the compressor clutch
relay and relay circuits. Repair the circuits or replace the
relay, if required.
5. See Electronic Cycling Clutch Switch in the Diagnosis
and Testing section of this group. Test the electronic
cycling clutch switch and replace, if required.
6. See Low Pressure Cut-Off Switch in the Diagnosis and
Testing section of this group. Test the low pressure cut-off
switch and replace, if required.
7. See High Pressure Cut-Off Switch in the Diagnosis and
Testing section of this group. Test the high pressure
cut-off switch and replace, if required.
8. Refer to the proper Diagnostic Procedures manual for
testing of the PCM. Test the PCM and replace, if
required.
9. See Heater-A/C Control in the Diagnosis and Testing
section of this group. Test the heater-A/C control and
replace, if required.

NORMAL PRESSURES,
BUT A/C
PERFORMANCE TEST
AIR TEMPERATURES
ARE TOO HIGH.

1. Excessive refrigerant
oil in system.
2. Temperature control
cable improperly installed
or faulty.
3. Blend-air door
inoperative, obstructed or
sealing improperly.

1. See Refrigerant Oil Level in the Service Procedures
section of this group. Recover the refrigerant from the
refrigerant system and inspect the refrigerant oil content.
Restore the refrigerant oil to the proper level, if required.
2. See Temperature Control Cable in the Removal and
Installation and Adjustments sections of this group.
Inspect the temperature control cable for proper routing,
operation and adjustment. Repair as required.
3. See Heater-A/C Housing Door in the Removal and
Installation section of this group. Inspect the blend-air
door for proper operation and sealing and correct, if
required.

DN

HEATING AND AIR CONDITIONING

24 - 13

DIAGNOSIS AND TESTING (Continued)