What should be done first when troubleshooting a non-operational air conditioning system?

When troubleshooting a non-operational air conditioning system, the most critical first step is checking the power supply to the unit. This is because many problems that cause an air conditioning system to stop functioning can be traced back to power issues. Before investigating more specific components like the thermostat, refrigerant levels, or maintenance history, ensuring that the unit is receiving power is essential.

A lack of power can manifest as the system not turning on at all or the controls being unresponsive. If power is not reaching the unit, further troubleshooting is pointless until that issue is resolved. Once you confirm that the air conditioner has power and is receiving the correct voltage, you can then move on to other potential issues with confidence.

In the broader context of troubleshooting, while checking thermostat settings, refrigerant levels, or reviewing maintenance logs is important, these steps can only be effectively pursued after eliminating power supply problems as a possible cause of the malfunction.