Bert’s starting point of the diagnostic process is the thermostat. The fan doesn’t respond, indicating that there is no power to the thermostat. However, the wiring appears to be correct. The issue isn’t at the float switch, and the breaker has been shut off instead of tripped. After Bert resets the breaker, the thermostat remains blank.

During Bert’s visual inspection, he determines that the fuse and low-voltage wiring connections are not the sources of the problem. However, the high-voltage wiring has been reading 0 volts even though there is power from one leg to ground. Bert resets the breakers, and nothing changes; there are 240v volts at the disconnect, so there appears to be an issue with the high-voltage connections.

After pulling the disconnect, Bert confirms that there is no power by checking the voltage to ground before he starts working on the wiring. Along the way, he gets distracted and forgets to put the disconnect back in after he resets the breakers.

Resetting the breaker does indeed give the unit high voltage, but the thermostat still isn’t receiving power. Bert changes the common wires, which appears to be the source of the problem. After putting the disconnect back in properly, Bert turns the thermostat on and notices that the unit is running. However, the unit is running in heat mode even though it’s supposed to be running in cool mode. The thermostat was reset to the settings for a furnace, not a heat pump, so Bert reprograms the thermostat correctly for the application.

Lesson learned: pay attention and don’t get distracted while filming your diagnosis.