ON-VEHICLE INSPECTION
PROCEDURE
1. INSPECT REFRIGERANT PRESSURE
(a) This method uses a refrigerant recovery unit set to locate problem areas. Read the refrigerant pressure when the test conditions are established.
Test conditions:
Gauge readings (Reference):
*a |
Pressure on low-pressure side |
*b |
Blower HI Zone |
*c |
Blower LO Zone |
*d |
Pressure on high-pressure side |
(1) Normally functioning refrigeration system. Gauge Reading:
|
|
(2) The A/C system periodically changes between normal and improper function due to moisture in the refrigerant system.
*a |
Low Pressure Side |
*b |
High Pressure Side |
Symptom |
Probable Cause |
Diagnosis |
Corrective Action |
---|---|---|---|
During operation, pressure on low pressure side cycles between normal and vacuum |
Moisture in refrigeration system freezes at expansion valve orifice, causing temporary stop of cycle. However, when melted, normal state is restored. |
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|
(3) The A/C system does not function effectively due to insufficient refrigerant.
*a |
Low Pressure Side |
*b |
High Pressure Side |
Symptom |
Probable Cause |
Diagnosis |
Corrective Action |
---|---|---|---|
|
Gas leakage from refrigeration system |
|
|
(4) The A/C system does not function effectively due to poor circulation of the refrigerant.
*a |
Low Pressure Side |
*b |
High Pressure Side |
Symptom |
Probable Cause |
Diagnosis |
Corrective Action |
---|---|---|---|
|
Refrigerant flow obstructed by dirt in condenser |
Condenser clogged |
Replace condenser |
(5) The A/C system does not function or functions intermittently because the refrigerant does not circulate.
*a |
Low Pressure Side |
*b |
High Pressure Side |
Symptom |
Probable Cause |
Diagnosis |
Corrective Action |
---|---|---|---|
|
|
Refrigerant does not circulate |
|
(6) The A/C system does not function effectively due to the system being overcharged with refrigerant or insufficient cooling of the condenser.
*a |
Low Pressure Side |
*b |
High Pressure Side |
Symptom |
Probable Cause |
Diagnosis |
Corrective Action |
---|---|---|---|
Pressure extremely high on both low and high-pressure sides |
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|
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(7) The A/C system does not function due to air in the refrigeration system.
CAUTION:
The low-pressure piping may be very hot and cause serious burns.
NOTICE:
These gauge indications occur when the refrigeration system opens and the system is charged with refrigerant without vacuum purging.
*a |
Low Pressure Side |
*b |
High Pressure Side |
Symptom |
Probable Cause |
Diagnosis |
Corrective Action |
---|---|---|---|
|
Air in refrigeration system |
|
|
(8) The A/C system does not function effectively due to an expansion valve malfunction.
*a |
Low Pressure Side |
*b |
High Pressure Side |
Symptom |
Probable Cause |
Diagnosis |
Corrective Action |
---|---|---|---|
|
Problem with expansion valve |
|
Replace expansion valve |
(9) The A/C system does not function due to a defective compressor.
*a |
Low Pressure Side |
*b |
High Pressure Side |
Symptom |
Probable Cause |
Diagnosis |
Corrective Action |
---|---|---|---|
|
Internal leakage in compressor |
|
Repair or replace compressor |
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