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JR
HEATING & AIR CONDITIONING (Continued)
TEMPERATURE REFERENCE CHART
Ambient
Temp.
Celsius
Fahrenheit
15.5°
60°
21.1°
70°
26.6°
80°
32.2°
90°
If the floor outlet air temperature is insufficient,
refer to 7 Cooling Systems for specifications. Both
heater hoses should be HOT to the touch (coolant
return hose should be slightly cooler than the supply
hose). If coolant return hose is much cooler than the
supply hose, locate and repair engine coolant flow
obstruction in heater system.
POSSIBLE CAUSE OF LOW OR OBSTRUCTED
COOLANT FLOW
(1) Pinched or kinked heater hoses.
(2) Improper heater hose routing.
(3) Plugged heater hoses or supply and return
ports at cooling system connections.
(4) Plugged heater core.
(5) Air locked heater core or air in cooling system.
(6) If coolant flow is verified and outlet tempera-
ture is insufficient, a mechanical problem may exist.
(7) Low coolant level.
(8) Low water pump flow.
POSSIBLE CAUSE OF INSUFFICIENT HEAT
(1) Obstructed cowl air intake.
(2) Obstructed heater system outlets.
(3) Blend-air door not functioning properly.
(4) Evaporator freeze up.
(5) Low coolant level.
(6) Air locked heater core or air in the cooling sys-
tem.
TEMPERATURE CONTROL
If temperature cannot be adjusted with the TEMP
knob on the control panel, the following could require
service:
(1) Blend-air door binding.
(2) Improper engine coolant temperature.
(3) Faulty Instrument Panel Control.
(4) Wiring or a fuse problem.
DIAGNOSIS AND TESTING - AIR
CONDITIONING SYSTEM
The air conditioning system is designed to remove
heat and humidity from the air entering the passen-
ger compartment. The evaporator, located in the
Minimum
Outlet
Floor
Temp.
Celsius
Fahrenheit
62.2°
144°
63.8°
147°
65.5°
150°
67.2°
153°
HEATING & AIR CONDITIONING
heater A/C unit, is cooled to temperatures near the
freezing point. As warm damp air passes over the
fins in the evaporator, moisture in the air condenses
to water, dehumidifying the air. Condensation on the
evaporator fins reduces the evaporators ability to
absorb heat. During periods of high heat and humid-
ity, an air conditioning system will be less effective.
With the control module set to RECIRC, only air
from the passenger compartment passes through the
evaporator. As the passenger compartment air dehu-
midifies, A/C performance levels rise.
PERFORMANCE
Review all Warnings before proceeding with this
procedure. Air temperature in test room and on vehi-
cle must be 21° C (70°F) minimum for this test.
NOTE: When connecting the service equipment
coupling to the line fitting, verify that the valve of
the coupling is fully closed. This will reduce the
amount of effort required to make the connection.
(1) Connect a tachometer and manifold gauge set
or a A/C Charging/Recycling Station. Attach a ther-
mocouple to the evaporator outlet line.
(2) Set controls:
MTC (Manual Temperature Control) System:
• A/C ON
• Panel Recirculation
• Temperature to full cold
• High blower
ATC (Automatic Temperature Control) System:
• Rotate blower knob to high position (full clock-
wise)
• Set temperature to the LO position
• Push panel mode button
• Push RECIRC (Recirculation) button (A/C and
RECIRC symbols should be lit)
NOTE: The word MANUAL should appear in the ATC
display, confirming that the system is set manually.
(3) Start engine and hold at 1000 rpm with A/C
clutch engaged.
(4) Engine should be warmed up with doors and
windows closed.
(5) Insert a thermometer or place a thermocouple
in the left center A/C outlet and operate the engine
for five minutes. The A/C clutch may cycle depending
on ambient conditions.
(6) With the A/C clutch engaged, compare the dis-
charge air temperature to the A/C Performance TEm-
perature table..
24 - 3
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