Cycling Clutch Switch Test

Cycling Clutch Switch And H Valve Assembly:

The cycling clutch switch is located on the refrigerant plumbing sealing plate ("H" valve area) and is electrically in series with the compressor clutch coil. It is an on-off switch which turns the compressor on and off depending on the temperature sensed by the Freon charged capillary tube. The capillary tube is inserted into a well located on the suction line. The well is filled with a special grease that is required for proper switch sensing. The switch is a sealed, specially calibrated unit and if found defective, must be replaced.

The low pressure cut-out (LPCO) Switch can produce rapid A/C compressor clutch cycling at low ambient temperatures or this can be a result of "H" valve failure. If A/C clutch cycling at low ambient temperatures is excessive while in the A/C or Defrost mode, manually pull out the A/C or Defrost mode button. This eliminates the compressor operation in that mode.

Testing
1. Remove wires from cycling clutch switch.
2. Check continuity of cycling clutch switch. Switch contacts are closed at temperatures above 7 °C (45 °F). If no continuity, replace switch.
3. If contacts are closed, verify switch operation as follows:
a. Reconnect wires to cycling clutch switch.
b. Set temperature control lever to full cool position.
c. Set A/C blower motor on LOW speed and push A/C button.
d. Operate engine at 1300 rpm for approximately 5 minutes to stabilize the A/C system.
e. If the compressor clutch cycles on and off 2 to 3 times per minute with temperature between 20 ° to 32 °C (68 ° to 90 °F), the cycling clutch switch is normal. If the compressor clutch fails to engage, check for an open in the electrical circuit. Above 32 °C (90 °F) the compressor clutch may be continuously engaged (non-cycling) due to the high heat load; this condition is normal.