Diagnosing Low-Pressure Side

1. Disconnect the electrical connector at the clutch cycling pressure switch and remove the switch from the switch fitting.

2. Install a new clutch cycling pressure switch and O-ring on the Tee Adapter Tool and plan to leave it on the Adapter as a permanent part of the tool. Be sure to lubricate O-ring before installation.

3. Install the Tee Adapter Tool on the clutch cycling pressure switch fitting and tighten it securely.

4. Connect the low-pressure hose of the manifold gauge set to the side fitting of the Tee Adapter Tool.

5. Connect the electrical connector to the clutch cycling pressure switch on the Tee Adapter Tool.

   With the Tee Adapter Tool installed in this manner the refrigerant system can be operated under normal conditions with clutch cycling pressure switch control and evaporator (suction) pressure can be observed. This will give a more accurate low-pressure reading than can be obtained from a low-pressure gauge port located in the suction line or near the compressor.

   After service is completed, disconnect the manifold gauge set from the Tee Adapter Tool. Disconnect the electrical connector from the clutch cycling pressure switch on the tool and remove the tool from the pressure switch fitting. Lubricate and install a new pressure switch O-ring. Install the removed clutch cycling pressure switch on the accumulator fitting and connect the electrical connector. Leak test the pressure switch attachment after installation.

   The diagnosis charts provide the most direct and sure way to determine the cause of any concern in a poorly performing refrigerant system.

   After servicing and correcting a refrigerant system concern, take additional pressure readings and observe the suction pressure and clutch cycle rate while meeting the conditional requirements from previous charts to ensure the condition has been corrected.

   In ambient temperatures above 26°C (80° F), the compressor clutch will not normally cycle off. This will depend on local conditions and engine/vehicle speed. Also, clutch cycling will normally not occur when the engine is operating at curb idle speed.

   If the system contains no refrigerant or is extremely low on refrigerant, the clutch will not engage for compressor operation. A rapid cycling compressor clutch is usually an indication that the system is low on refrigerant. Refer to Insufficient or No A/C Cooling—Fixed Orifice Tube Cycling Clutch System Diagnosis chart.

   The following tests cover trouble-causing items such as: burned out fuses, loose wire connections, damaged wires, or collapsed hoses.