Performance Diagnosis of A/C System: Notes

WARNING: This page is about a different car, the 2004 Suzuki Vitara. However, it is still accessible from the selected car via links, so may be relevant.

Confirm that vehicle and environmental conditions are as follows.
- Vehicle is not exposed to direct sun.
- Ambient temperature is within 15 - 35°C (59 - 95°F).
Make sure that high pressure valve (1) and low pressure valve (2) of manifold gauge are firmly closed.
Connect high pressure charging hose (3) to high pressure service valve (5) on vehicle, and connect low pressure charging hose (4) to low pressure service valve (6) on vehicle.
Bleed the air in charging hoses ((3), (4)) by loosening their respective nuts on manifold gauge, utilizing the refrigerant pressure. When a hiss is heard, immediately tighten nut.
CAUTION: Do not interchange high and low pressure charging hoses by mistake.

Fig 1: Identifying A/C System Components
Courtesy of SUZUKI OF AMERICA CORP.
Warm up engine to normal operating temperature (engine coolant temperature at 80 - 90°C (176 - 194°F)) and keep it at specified idle speed. (Radiator cooling fan should not be working when checking pressure and temperature.)
Turn A/C switch ON, and set blower switch at "HI" (4th position), temperature control knob at "COOL", air outlet control knob at "FACE", fresh/circulation control knob at "CIRCULATION". (Confirm that A/C compressor and condenser fan are working.)
Performance test condition

Fig 2: Performance Test Condition Chart
Courtesy of SUZUKI OF AMERICA CORP.
Keep all windows, doors and engine food open.
With about 20 mm (0.8 in.) of dry bulb thermometer (1) inserted into center duct air outlet and another one set near evaporator air inlet, read temperature indicated on each thermometer.

Fig 3: Identifying Dry Bulb Thermometer
Courtesy of SUZUKI OF AMERICA CORP.
Check for each pressure of low side and high side if it is within shaded range of graph.
If each gauge reading is out of specified pressure, correct defective part referring to "PERFORMANCE DIAGNOSIS TABLE: ".

Example:

Fig 4: Gauge Reading Reference Chart
Courtesy of SUZUKI OF AMERICA CORP.

NOTE: Pressure registered on gauge varies with ambient temperature. Therefore, use the graphs when determining if pressures are normal or not.

Fig 5: Ambient Temperature - Gauge Pressure Graph
Courtesy of SUZUKI OF AMERICA CORP.
Check inlet port temperature-to-outlet port temperature relationship using graph.
For example, if evaporator inlet port temperature is 25°C (77°F) and center duct air outlet temperature is 8°C (46.4°F), their crossing point is within acceptable range as shown in graph.

Fig 6: Inlet Port Temperature-To-Outlet Port Temperature Relationship Graph
Courtesy of SUZUKI OF AMERICA CORP.
If crossing point is out of acceptable range, diagnose trouble referring to "PERFORMANCE DIAGNOSIS TABLE: ".