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24 - 10
HEATING AND AIR CONDITIONING
DESCRIPTION AND OPERATION (Continued)
A manifold gauge set may be needed with some
recovery/recycling/charging equipment (Fig. 6). 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.
Fig. 6 Manifold Gauge Set - Typical
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 liquid line near the evaporator inlet
tube at the rear of the engine compartment.
HIGH PRESSURE GAUGE HOSE
The high pressure hose (Red with Black stripe)
attaches to the discharge service port. This port is
located on the manifold directly over the discharge
port of the compressor.
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.
REFRIGERANT SYSTEM SERVICE PORT
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.
The high pressure service port is located on the
refrigerant line manifold, near the discharge port of
the compressor. The low pressure service port is
located on the liquid line at the rear of the engine
compartment, near the evaporator inlet tube.
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
A vacuum check valve is installed in the accessory
vacuum supply line in the engine compartment, near
the vacuum tap on the engine intake manifold. The
vacuum check valve is designed to allow vacuum to
flow in only one direction through the accessory vac-
uum supply circuits.
The use of a vacuum check valve helps to maintain
the system vacuum needed to retain the selected
heater-A/C mode settings. The check valve 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 valve cannot be repaired and, if
faulty or damaged, it must be replaced.
VACUUM RESERVOIR
The vacuum reservoir is mounted to the rear of the
right front inner fender wheelhouse in the engine
compartment, under the battery tray. The battery
and battery tray must be removed from the vehicle to
access the vacuum reservoir for service.
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.
TJ
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