Dodge RAM TRUCK 1500 1995 Service Manual page 1671

24 - 2 HEATING AND AIR CONDITIONING
AIR CONDITIONING SYSTEM
The A/C system uses a SD7H15 fixed displacement
compressor. A label identifying the use of R-134a re­
frigerant is located on the compressor.
The air conditioning system has an evaporator to
cool and dehumidify the incoming outside air prior to
blending with the heated air. The compressor is in
operation during the FLOOR/DEFROST mode, DE­
FROST mode and when the blower speed switch is in
the A/C (blue) section. The compressor is not in oper­
ation at ambient temperatures below approximately
-1°C (30°F). To maintain minimum evaporator tem­
perature, a fixed pressure setting switch cycles the
compressor clutch. The blower is operating in the
heater or air conditioning systems, except in the OFF
mode. In the OFF mode the blower and the outside
air are shut off.
SYSTEM AIRFLOW
Refer to Fig. 3 for the system airflow. The system
pulls outside (ambient) air through the cowl opening
at the base of the windshield. Then it goes into the
plenum chamber above the heater-A/C housing. On
air conditioned vehicles, the air passes through the
evaporator. Air flow can be directed either through or
around the heater core. This is done by adjusting the
blend-air door with the TEMP control on the instru­
ment panel. The air flow can then be directed from
the PANEL, BI-LEYEL (panel and floor), FLOOR,
FLOOR/DEFROST or DEFROST outlets. Air flow ve­
locity can be adjusted with the blower speed selector
switch on the instrument panel.
DEFROST
OUTLET
OUTSIDE
AIR INLET
PANEL
OUTLET
FLOOR
OUTLET
RECIRCULATION
INLET
J9424-29
Fig. 3 Heater-A/C System Airflow (Front View)
On air conditioned vehicles, outside air can be shut
off by opening the recirculating air door. This will re­
circulate the air that is already inside the vehicle.
This is done by rotating the MODE control knob into
the RECIRC position.
A/C COMPONENTS
ACCUMULATOR: The Accumulator is mounted in
the engine compartment on the right side of the ve­
hicle. The inlet tube of the accumulator attaches di­
rectly to the evaporator core outlet tube. Refrigerant
enters the accumulator canister through the inlet
tube. The liquid oil-laden refrigerant falls to the bot­
tom of the canister which acts as a separator. A des-
iccant bag is mounted inside the suction accumulator
canister to absorb any moisture which may be in the
refrigerant system (Fig.4).
INLET FROM EVAPORATOR
O-RING SEAL
ACCUMULATOR DOME
VAPOR RETURN
TUBE
OIL RETURN
ORIFICE FILTER
CLUTCH CYCLING
PRESSURE SWITCH
PRESSURE SWITCH
FITTING
OUTLET TO
COMPRESSOR
ANTI-SIPHON
HOLE
DESICCANT BAG
J9324-6
Fig. 4 Accumulator
COMPEESSOE: The SD7H15 Compressor is used
on all models. The purpose of the compressor is to
compress the low-pressure refrigerant vapor into a
high pressure, high temperature vapor. The compres­
sor is serviced as a assembly only.
CLUTCH PULLEY AND COIL: They are
mounted on the compressor and providing a way to
drive the compressor. The compressor clutch and coil
are the only serviced parts on the SD7H15 compres­
sor. When the compressor is not in operation, the
pulley free wheels on the clutch hub bearing. When
the coil is energized the clutch plate is magnetically
engaged with the pulley and turns the compressor
shaft.
AIR CONDITIONING CYCLING SWITCH: The
switch is mounted on top of the accumulator. The
switch is wired in series with compressor clutch. The