■ Check condensing unit to see if it is operating. Place one hand on the liquid line and the other on suction line. If the condenser fan is operational and there isn’t any difference in the temperature of the two lines, the compressor is not operating. If the fan motor is not operating, check for line voltage and low voltage in the control panel. You must establish if the problem is in line voltage or low voltage. If line voltage is present, and there is no low voltage, nothing will operate.
No line voltage— Check fuses for the supply voltage to the condensing unit.
No low voltage— If present through the thermostat, a wire from the thermostat to the condensing unit is open.
tests can be made over a period of time. In the above case, the pressure recorder hooked to the high side of the system. The amperage recorder should be hooked to the condenser fan motor power supply. Each time the compressor cycles on, the pressure is recorded on a chart similar to those used in the medical profession. Everytime the compressor cycles so should the condenser fan motor. The defective motor will stop operating and thus the amperage will either fall to zero or climb to locked rotor and fall. This would be followed by the high pressure side of the system starting to elevate. This is truly the only way to solve a situation such as this.