Low Pressure Cut-Off Switch; Rear Overhead Air Conditioner; Refrigerant; Refrigerant Lines - Dodge 2000 DURANGO Service Manual

DN
DESCRIPTION AND OPERATION (Continued)
turbed. The valve is only serviced as a part of the
compressor assembly.

LOW PRESSURE CUT-OFF SWITCH

DESCRIPTION
The low pressure cut-off switch is located on the
suction line jumper tube. The switch is screwed onto
a fitting that contains a Schrader-type valve, which
allows the switch to be serviced without discharging
the refrigerant system. The fitting is equipped with
an O-ring to seal the switch connection.
OPERATION
The low pressure cut-off switch is connected in
series electrically with the high pressure cut-off
switch, the heater-A/C
Cycling Clutch Switch (ECCS), between ground, and
the Powertrain Control Module (PCM). The switch
contacts open and close causing the PCM to turn the
compressor clutch on and off. This regulates the
refrigerant system pressure, ensuring a sufficient
amount of refrigerant throughout the system.
The low pressure cut-off switch contacts will open
when the suction pressure is about 48 to 90 kPa (7 to
13 psi) or lower. The switch contacts will close when
the suction pressure rises to about 103 to 193 kPa
(15 to 28 psi) or above. Lower ambient temperatures,
below about -1° C (30° F), will also cause the switch
contacts to open. This is due to the pressure/temper-
ature relationship of the refrigerant in the system.
The low pressure cut-off switch is a factory-cali-
brated unit. It cannot be adjusted or repaired and, if
faulty or damaged, it must be replaced.

REAR OVERHEAD AIR CONDITIONER

DESCRIPTION
A rear overhead air conditioning unit is an avail-
able option to supplement the output of the front air
conditioner, for increased rear seat passenger com-
fort. This unit includes a roof-mounted evaporator
coil and a blower motor with a wide squirrel-cage
type blower wheel. A four position (three speeds plus
off) rear blower motor switch is mounted in the head-
liner behind the right front seat position, where it is
accessible to both the driver and the second seat pas-
sengers.
OPERATION
The wide and shallow rear unit is positioned
between the front and second seats to provide ample
headroom for all vehicle occupants. The headliner is
molded to cover the unit and includes an integral air
intake grille toward the front of the unit, and an
opening for a snap-in outlet bezel that includes four
controls, the Electronic
HEATING AND AIR CONDITIONING
adjustable outlet barrels toward the rear of the unit.
A condensate tray is integral to the lower unit hous-
ing, and water is drained out of the unit through
hoses located behind the trim on each of the B-pil-
lars.
The rear overhead air conditioner will provide cool-
ing only when an air conditioning mode is selected
with the front heater and A/C controls, but the rear
blower will operate independent of the front controls
to circulate the interior air if desired.

REFRIGERANT

DESCRIPTION
The refrigerant used in this air conditioning sys-
tem is a HydroFluoroCarbon (HFC), type R-134a.
Unlike R-12, which is a ChloroFluoroCarbon (CFC),
R-134a refrigerant does not contain ozone-depleting
chlorine. R-134a refrigerant is a non-toxic, non-flam-
mable, clear, and colorless liquefied gas.
Even though R-134a does not contain chlorine, it
must be reclaimed and recycled just like CFC-type
refrigerants. This is because R-134a is a greenhouse
gas and can contribute to global warming.
OPERATION
R-134a refrigerant is not compatible with R-12
refrigerant in an air conditioning system. Even a
small amount of R-12 added to an R-134a refrigerant
system will cause compressor failure, refrigerant oil
sludge or poor air conditioning system performance.
In addition, the PolyAlkylene Glycol (PAG) synthetic
refrigerant oils used in an R-134a refrigerant system
are not compatible with the mineral-based refriger-
ant oils used in an R-12 refrigerant system.
R-134a refrigerant system service ports, service
tool couplers and refrigerant dispensing bottles have
all been designed with unique fittings to ensure that
an R-134a system is not accidentally contaminated
with the wrong refrigerant (R-12). There are also
labels posted in the engine compartment of the vehi-
cle and on the compressor identifying to service tech-
nicians that the air conditioning system is equipped
with R-134a.

REFRIGERANT LINES

DESCRIPTION
The refrigerant lines and hoses are used to carry
the refrigerant between the various air conditioning
system components. A barrier hose design with a
nylon tube, which is sandwiched between rubber lay-
ers, is used for the R-134a air conditioning system on
this vehicle. This nylon tube helps to further contain
the R-134a refrigerant, which has a smaller molecu-
lar structure than R-12 refrigerant. The ends of the
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