Procedure 2 - Ambient Temperature Above 38°C (100°F)
WARNING: This page is about a different car, the 2011 Mercury Milan, 2011 Lincoln MKZ, and 2011 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
The system performance can be evaluated and diagnosed by analysis of the compressor suction and discharge pressures. The following procedure is used to determine if the system is operating at normal pressures.
NOTE:
The procedure varies depending on the ambient (shop) temperature. If the ambient temperature is 38°C (100°F) or lower, follow Procedure 1. If the ambient temperature is over 38°C (100°F), follow Procedure 2.
- Drive the vehicle or run the engine until it reaches normal operating temperature.
- Connect a R-134a Manifold Gauge Set or R-134a Refrigerant Management Machine with high-pressure and low-pressure gauges to the refrigerant system.
- Set the climate controls.
- If equipped with manual climate control, set the A/C controls for normal A/C-PANEL mode, full COOL temperature, FRESH air, MED-LO blower. If the vehicle has a fresh air/recirc button, set it to FRESH. If the vehicle has an A/C switch or compressor on switch, set it to A/C ON.
- If equipped with Electronic Automatic Temperature Control (EATC) or Dual Automatic Temperature Control (DATC), set temperature to 15°C (60°F) (lowest possible temp setting). Manually set blower to MED-LO (3 to 4 bars). If the vehicle has a fresh air/recirc button, set it to FRESH. If the vehicle has an A/C switch or compressor on switch, set it to A/C ON.
- Open all vehicle windows and leave the hood open for the test. Open the rear hatch and/or rear doors (if equipped).
- Confirm the compressor clutch is engaged and the engine cooling fan(s) are operating or engaged. Allow the vehicle to idle until the suction (low-side) and discharge (high-side) pressures are stable or fluctuate in a range that repeats.
- Record the ambient (shop) temperature.
- Record the discharge pressure. If the pressure is fluctuating, record the average value.
- Determine if the discharge pressure falls within the normal operating limits using the Normal Refrigerant Discharge Pressures chart.
- Record the suction pressure. If the pressure is fluctuating, record the average value.
- Determine if the suction pressure falls between normal operating limits using the Normal Refrigerant Suction Pressures chart.
- Proceed to the Diagnostic Table below.
Diagnostic Table
- Refer to the chart below.
NOTE:
The following table is used to guide diagnosis of the refrigerant system if operating pressures are outside normal limits.
Diagnostic Table
| High (Discharge) Pressure | Low (Suction) Pressure | Component - Causes | ||||
|---|---|---|---|---|---|---|
| High or Clutch Cycling | High | Condenser - inadequate airflow. | ||||
| High | Normal to High | Engine - overheating. | ||||
| Normal to High | Normal | Refrigerant overcharge - air in refrigerant. | ||||
| Normal to Low | Normal to High | A/C suction line - partially restricted or plugged. (1) | ||||
| Normal to Low | Low or Clutch Cycling | Low refrigerant charge, A/C suction line - partially restricted or plugged A/C evaporator discharge air temperature sensor - reading erratic or low (if equipped).(2) | ||||
| Erratic Operation or Compressor Not Running | A/C evaporator discharge air temperature sensor - poor connection at A/C clutch connector or A/C evaporator discharge air temperature sensor connector. A/C electrical circuit erratic - see SYSTEM WIRING DIAGRAMS article, A/C Electrical Circuit. | |||||
| Normal to Low | High | Compressor - low performance. | ||||
| Additional Possible Cause Components Associated With Inadequate Compressor Operation | ||||||
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| Additional Possible Cause Components Associated With a Damaged Compressor | ||||||
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