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Air Conditioning (A/C) System Performance Test

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
System Condition Charts - Definition and Usage

Degrees* Suction* Discharge* Outlet*
21°C (70°F) 131-186 kPa (19-27 psi) 765-1130 kPa (111-164 psi) 1-8°C (33-46°F)
27°C (80°F) 131-186 kPa (19-27 psi) 896-1193 kPa (130-173 psi) 1-9°C (33-49°F)
33°C (90°F) 131-186 kPa (19-27 psi) 1151-1462 kPa (167-212 psi) 2-9°C (34-49°F)
38°C (100°F) 144-193 kPa (21-28 psi) 1456-1751 kPa (211-254 psi) 3-10°C (37-51°F)
43°C (110°F) 144-193 kPa (21-28 psi) 1599-1938 kPa (232-281 psi) 3-10°C (37-51°F)
IMPORTANT: Statements contain additional information to help you confirm your diagnosis and lead you to a corrective action.
When ALL pressure and temperature readings fall within the ranges of a given chart, use that chart to repair the vehicle.
Key: Statements are used to interpret the pressure and temperature readings compared to normal system performance. If testing above or below ambient temperatures listed, rely on key statements to diagnose system.Then: Statements contain additional information to help you confirm your diagnosis and lead you to a corrective action. When all pressure and temperature readings fall within the ranges of a given chart, use that chart to repair the vehicle.*Degrees - If the ambient air temperature is*Suction - and the low side gage should read*Discharge - and the high side gage should read*Outlet - and the right center air temperature should be
Normal System Performance Service Stall

Degrees* Suction* Discharge* Outlet*
21°C (70°F) 131-186 kPa (19-27 psi) 765-1130 kPa (111-164 psi) 1-8°C (33-46°F)
27°C (80°F) 131-186 kPa (19-27 psi) 896-1193 kPa (130-173 psi) 1-9°C (33-49°F)
33°C (90°F) 131-186 kPa (19-27 psi) 1151-1462 kPa (167-212 psi) 2-9°C (34-49°F)
38°C (100°F) 144-193 kPa (21-28 psi) 1456-1751 kPa (211-254 psi) 3-10°C (37-51°F)
43°C (110°F) 144-193 kPa (21-28 psi) 1599-1938 kPa (232-281 psi) 3-10°C (37-51°F)
*Degrees - If the ambient air temperature is
*Suction - and the low side gage should read
*Discharge - and the high side gage should read
*Outlet - and the right center air temperature should be
IMPORTANT: To ensure accurate pressure and temperature readings make sure the vehicle is properly set up to run the performance test. Refer to vehicle set up section in this manual. ALL TEST PARAMETERS MUST BE FOLLOWED TO OBTAIN ACCURATE READINGS.
IMPORTANT: Use a refrigerant identifier to verify refrigerant purity. Non-condensable gases or refrigerant substitutes will affect system pressure/temperature readings.
Normal System Performance Service Stall High Humidity

Degrees* Suction* Discharge* Outlet*
21°C (70°F) 138-193 kPa (20-28 psi) 807-1124 kPa (117-163 psi) 2-9°C (36-48°F)
27°C (80°F) 138-193 kPa (20-28 psi) 1075-1358 kPa (156-197 psi) 2-10°C (36-50°F)
33°C (90°F) 144-193 kPa (21-28 psi) 1489-1793 kPa (216-260 psi) 5-12°C (40-53°F)
38°C (100°F) 144-193 kPa (21-28 psi) 1627-1994 kPa (236-289 psi) 6-13°C (43-55°F)
43°C (110°F) 144-200 kPa (21-29 psi) 1917-2303 kPa (278-334 psi) 6-14°C (43-56°F)
*Degrees - If the ambient air temperature is
*Suction - and the low side gage should read
*Discharge - and the high side gage should read
*Outlet - and the right center air temperature should be
General System Condition - Low Refrigerant Charge

Degrees* Suction* Discharge* Outlet*
21-43°C (70-110°F) Normal to High Low Slightly Cool to Warm
Key: Poor Cooling at Higher Ambients.
Then: The system is operating with a low charge.
  • Leak test all the components and connections.
  • If the refrigerant charge level is unknown, reclaim, evacuate and recharge the system with 0.68 kg (1.5 lb) of R-134a.
  • Run another performance test.

*Degrees - If the ambient air temperature is
*Suction - and the low side gage should read
*Discharge - and the high side gage should read
*Outlet - and the right center air temperature should be
General System Condition Refrigerant/Oil Overcharge

Degrees* Suction* Discharge* Outlet*
21-43°C (70-110°F) Normal to Slightly High High Cool to Warm
Key: The high pressures cause the pressure sensor to cycle the compressor on and off at high ambient air temperatures
Then: The System may be operating in an overcharged condition.
  • An overcharged condition will generate a poor and/or intermittent cooling complaint at higher ambient air temperatures. Intermittent complaints are caused by the pressure sensor cycling the compressor OFF and ON.
  • Reclaim the system using an approved recovery system. Evacuate and recharge the system with 0.68 kg (1.5 lb) of R-134a.
  • Run another performance test.
  • An oil overcharge can occur if a compressor or other refrigerant system change is made without proper oil balancing. Review the vehicle service history for compressor service.

*Degrees - If the ambient air temperature is
*Suction - and the low side gage should read
*Discharge - and the high side gage should read
*Outlet - and the right center air temperature should be
Specific System Condition - Compressor No-Pump

Degrees* Suction* Discharge* Outlet*
21-43°C (70-110°F) 483-689 kPa (70-100 psi) 483-689 kPa (70-100 psi) 21-43°C (70-110°F)
IMPORTANT: Ensure that the manifold gage set valves are closed.
Key: No change in the suction and the discharge pressures with the compressor engaged. The gage pressures will be almost equal.Then:
  • Verify compressor clutch engagement.
  • Run the engine at 2,000 RPM and cycle the compressor ON and OFF two or three times.
  • If the pressure remains static, engage the compressor and snap the engine throttle two or three times.
  • If the pressure still remains static, replace the compressor.
  • After the repair, return to the diagnostic flow chart.
*Degrees - If the ambient air temperature is*Suction - and the low side gage should read*Discharge - and the high side gage should read*Outlet - and the right center air temperature should be
Specific System Condition - Compressor at Minimum Displacement

Degrees* Suction* Discharge* Outlet*
21°C (70°F) 165-207 kPa (24-30 psi) 730-1007 kPa (106-146 psi) 2-8°C (35-47°F)
27°C (80°F) 172-213 kPa (25-31 psi) 834-1110 kPa (121-161 psi) 3-9°C (37-49°F)
33°C (90°F) 199-241 kPa (29-35 psi) 930-1207 kPa (135-175 psi) 5-9°C (42-49°F)
38°C (100°F) 220-275 kPa (32-40 psi) 1145-1421 kPa (166-206 psi) 7-12°C (45-54°F)
43°C (110°F) 220-275 kPa (32-40 psi) 1158-1434 kPa (168-208 psi) 7-12°C (45-54°F)
Key:
  • Increased suction pressure for a relatively low discharge pressure.
  • High outlet temperatures.

Then: The compressor may be at minimum displacement.
  • This condition will be most noticeable at high ambients.
  • Confirm the charge level before replacing the compressor.
  • After the repair, return to the diagnostic flow chart.
Specific System Condition - Compressor at Maximum Displacement

Degrees* Suction* Discharge* Outlet*
21-43°C (70-110°F) Low to Normal High Cold
Key:
  • Lower than normal suction pressure and outlet temperature at lower ambients.
  • Higher than normal discharge pressures.

Then: The compressor may be at maximum displacement.
  • This condition will be most noticeable at low ambients.
  • This condition could create a compressor cycling complaint due to the Evaporator Low Ambient Protection (ELAP) cycling the compressor to prevent evaporator freeze. On L61 equipped vehicles, this cycling condition may not be duplicated in the service stall testing.
  • Replace the compressor.
  • After the repair, return to the diagnostic flow chart.

*Degrees - If the ambient air temperature is
*Suction - and the low side gage should read
*Discharge - and the high side gage should read
*Outlet - and the right center air temperature should be
Specific System Condition - TXV Open

Degrees* Suction* Discharge* Outlet*
21-43°C (70-110°F) Normal to Slightly High Normal to Slightly High Cool to Warm
Key:
  • Higher than normal suction pressure.
  • Higher than normal outlet temperature.
  • Hissing or gurgling noise may be observed near the TXV.

Then: The thermal expansion valve (TXV) may be open.
  • Replace the TXV.
  • After the repair, return to the diagnostic flow chart.

*Degrees - If the ambient air temperature is
*Suction - and the low side gage should read
*Discharge - and the high side gage should read
*Outlet - and the right center air temperature should be
Specific System Condition - TXV Restricted or Closed

Degrees* Suction* Discharge* Outlet*
21-43°C (70-110°F) Low Low Cool to Warm
Key:
  • Near vacuum for suction pressure.
  • Low discharge pressure.
  • Right center air outlet near ambient.

Then: The thermal expansion valve (TXV) may be restricted or closed.
  • Replace the TXV.
  • After the repair, return to the diagnostic flow chart.

*Degrees - If the ambient air temperature is
*Suction - and the low side gage should read
*Discharge - and the high side gage should read
*Outlet - and the right center air temperature should be
General System Condition - High or Low Side Restrictions

Degrees* Suction* Discharge* Outlet*
21-43°C (70-110°F) Low Low Cool to Warm
Key:
  • Temperature drop across restriction in line or component.
  • Frost may be observed near the restriction.

Then: Confirm the condition by a thorough physical and visual inspection of all lines and components.
  • The temperature will be much colder on the down stream side of the restriction. Also look for possible frost.
  • Replace the restricted part.
  • After the repair, return to the diagnostic flow chart.

*Degrees - If the ambient air temperature is
*Suction - and the low side gage should read
*Discharge - and the high side gage should read
*Outlet - and the right center air temperature should be
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