A/C Diagnosis
CONDITION POSSIBLE CAUSE CORRECTION
LOW SIDE PRESSURE
IS NORMAL OR
SLIGHTLY LOW, AND
HIGH SIDE PRESSURE
IS TOO LOW.
1. Low refrigerant system
charge.
2. Refrigerant flow
through the evaporator
coil is restricted.
3. Faulty compressor.
1. See Refrigerant System Leaks in the Diagnosis and
Testing section of this group. Test the refrigerant system
for leaks. Repair, evacuate and charge the refrigerant
system, if required.
2. See Evaporator Coil in the Removal and Installation
section of this group. Replace the restricted evaporator
coil, if required.
3. See Compressor in the Diagnosis and Testing section
of this group. Replace the compressor, if required.
LOW SIDE PRESSURE
IS NORMAL OR
SLIGHTLY HIGH, AND
HIGH SIDE PRESSURE
IS TOO HIGH.
1. Condenser air flow
restricted.
2. Inoperative cooling
fan.
3. Faulty expansion
valve.
4. Refrigerant system
overcharged.
5. Air in the refrigerant
system.
6. Engine overheating.
1. Check the condenser for damaged fins, foreign objects
obstructing air flow through the condenser fins, and
missing or improperly installed air seals. Refer to Group 7
- Cooling System for more information on air seals.
Clean, repair, or replace components as required.
2. Refer to Group 7 - Cooling System for more
information. Test the cooling fan and replace, if required.
3. See Expansion Valve in the Diagnosis and Testing
section of this group. Replace the faulty expansion valve,
if required.
4. See Refrigerant System Charge in the Service
Procedures section of this group. Recover the refrigerant
from the refrigerant system. Charge the refrigerant
system to the proper level, if required.
5. See Refrigerant System Leaks in the Diagnosis and
Testing section of this group. Test the refrigerant system
for leaks. Repair, evacuate and charge the refrigerant
system, if required.
6. Refer to Group 7 - Cooling System for more
information. Test the cooling system and repair, if
required.
LOW SIDE PRESSURE
IS TOO HIGH, AND
HIGH SIDE PRESSURE
IS TOO LOW.
1. Accessory drive belt
slipping.
2. Faulty compressor.
1. Refer to Group 7 - Cooling System for more
information. Inspect the accessory drive belt condition
and tension. Tighten or replace the accessory drive belt, if
required.
2. See Compressor in the Diagnosis and Testing section
of this group. Replace the compressor, if required.
LOW SIDE PRESSURE
IS TOO LOW, AND HIGH
SIDE PRESSURE IS
TOO HIGH.
1. Restricted refrigerant
flow through the
refrigerant lines.
2. Restricted refrigerant
flow through the
expansion valve.
3. Restricted refrigerant
flow through the
condenser.
4. Restricted refrigerant
flow through the
filter-drier.
1. See Liquid Line and Suction and Discharge Line in the
Removal and Installation section of this group. Inspect the
refrigerant lines for kinks, tight bends or improper routing.
Correct the routing or replace the refrigerant line, if
required.
2. See Expansion Valve in the Diagnosis and Testing
section of this group. Replace the restricted expansion
valve, if required.
3. See Condenser in the Removal and Installation section
of this group. Replace the restricted condenser, if
required.
4. See Filter-Drier in the Removal and Installation section
of this group. Replace the restricted filter-drier, if required.
24 - 14 HEATING AND AIR CONDITIONING DN
DIAGNOSIS AND TESTING (Continued)
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