Diagnostic Table

WARNING: This page is about a different car, the 2005 Mercury Sable and 2005 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: The following table is used to guide diagnosis of the refrigerant system if operating pressures are outside normal limits.

Refer to the chart below.

A/C PRESSURE TROUBLESHOOTING

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	High	Fixed orifice tube - missing O-rings leaking/missing.
Normal to Low	Normal to High	A/C suction line - partially restricted or plugged^a .
Normal to Low	Low or Clutch Cycling	Low refrigerant charge, A/C suction line - partially restricted or plugged^b A/C cycling switch - sticking closed (if equipped).
Erratic Operation or Compressor Not Running		A/C cycling switch - poor connection at A/C clutch connector or clutch cycling switch connector. A/C electrical circuit erratic - see A/C Electrical Circuit Wiring Diagram.
Normal to Low	High	Compressor - low performance.
Additional Possible Cause Components Associated With Inadequate Compressor Operation
Compressor Drive Belt - loose Compressor Clutch - slipping Clutch Coil Open - shorted, or loose mounting Control Assembly Switch - dirty contacts or sticking open Clutch Wiring Circuit - high resistance, open or blown fuse Compressor Operation Interrupted by Engine Computer
Additional Possible Cause Components Associated With a Damaged Compressor
Incorrect Clutch Air-gap Suction Accumulator - refrigerant oil bleed hose plugged Refrigerant Leaks
a Low pressure reading will be normal to high if pressure is taken at accumulator and if restriction is downstream of service access valve.
b Low pressure reading will be low if pressure is taken near the compressor and restriction is upstream of service access valve.