Condition
Possible Causes
Correction
The low side pressure is
normal or slightly high, and
the high side pressure is too
high.
1. Condenser air flow
restricted.
1. Check the A/C condenser for damaged fins,
foreign objects obstructing air flow through the
condenser fins, and missing or improperly
installed air seals. Refer to Cooling for more
information on air seals. Clean, repair, or replace
components as required.
2. Inoperative cooling fan.
2. Refer to Cooling for more information. Test the
cooling fan and replace, if required.
3. Refrigerant system
overcharged.
3. See Refrigerant System Charge in this group.
Recover the refrigerant from the refrigerant
system. Charge the refrigerant system to the
proper level, if required.
4. Air in the refrigerant
system.
4. See Refrigerant System Leaks in this group.
Test the refrigerant system for leaks. Repair,
evacuate and charge the refrigerant system, if
required.
5. Engine overheating.
5. Refer to Cooling for more information. Test the
cooling system and repair, if required.
The low side pressure is too
high, and the high side
pressure is too low.
1. Accessory drive belt
slipping.
1. Refer to Cooling for more information. Inspect
the accessory drive belt condition and tension.
Tighten or replace the accessory drive belt, if
required.
2. Fixed orifice tube not
installed.
2. See A/C Orifice Tube in this group. Replace
the liquid line, if required.
3. Faulty compressor.
3. See A/C Compressor in this group. Replace
the compressor, if required.
The low side pressure is too
low, and the high side
pressure is too high.
1. Restricted refrigerant flow
through the refrigerant lines.
1. See Liquid, Suction, and Discharge Line in this
group. Inspect the refrigerant lines for kinks, tight
bends or improper routing. Correct the routing or
replace the refrigerant line, if required.
2. Restricted refrigerant flow
through the fixed orifice tube.
2. See A/C Orifice Tube in this group. Replace
the liquid line, if required.
3. Restricted refrigerant flow
through the condenser.
3. See A/C Condenser in this group. Replace the
restricted condenser, if required.
HEATER PERFORMANCE
Before performing the following tests, refer to Group 7 - Cooling for the procedures to check the engine coolant
level and flow, engine coolant reserve/recovery system operation, accessory drive belt condition and tension, radi-
ator air flow and the fan drive operation. Perform the HVAC System Test (refer to 24 - HVAC Electrical Diagnostics).
If any diagnostic trouble codes (DTCs) are found in the A/C-heater control or the powertrain control module (PCM),
repair as necessary.
MAXIMUM HEATER OUTPUT: TEST AND ACTION
Engine coolant is provided to the heater system through two heater hoses. With the engine idling at normal oper-
ating temperature, set the temperature control to maximum heat position, the mode control to the floor position, and
the blower motor control to the highest speed position. Using a test thermometer, check the temperature of the air
being discharged from the floor outlets. Compare the test thermometer reading to the Heater Temperature Refer-
ence chart.
24 - 196
HVAC - SERVICE INFORMATION
DR/DH