I was called to a home to repair an HVAC unit that was not turning on. Upon arrival, I found that the unit was not receiving power. I checked the circuit breaker and found that it was tripped. I reset the breaker and tried to turn on the unit again, but it still did not work. I checked the wiring and found that one of the wires was loose. I tightened the wire and tried to turn on the unit again, and it started up. I tested the unit to ensure that it was working properly and left the home.