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
24 - 24 HEATING AND AIR CONDITIONING DN
DIAGNOSIS AND TESTING (Continued)
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