In this troubleshooting situation, the customer’s complaint is that their office air conditioner is “not cooling at all.” When you arrive, you confirm that the indoor air temperature is far above the standard comfort level, that the indoor fan motor is operating, and that the thermostat is properly set to call for cooling.

The first thing you note when checking this rooftop unit is that the lockout relay system has done its job of shutting down the compressor operation (note the schematic in Figure One), and you also note that neither outdoor fan motor is operating.