A technician finds that a system does not operate when the thermostat calls for cooling. What is the first check the technician should perform?

When a technician encounters a situation where a system does not operate upon the thermostat's call for cooling, the first step of verifying the thermostat settings is crucial. This step is fundamental because it addresses the most immediate and straightforward factor that could prevent the system from functioning.

Thermostats can sometimes be set incorrectly, whether by being mistakenly adjusted to a higher temperature than the room or being switched to a heating rather than cooling mode. Ensuring the thermostat is correctly set helps eliminate simple user error as the source of the issue, which can save time and unnecessary troubleshooting of more complex components.

If the thermostat settings are correct, the technician can then proceed to check other aspects of the system, such as the compressor functionality, inspecting the circuit breaker, or measuring voltage, knowing that the initial simple check has been addressed. This method of beginning with the most basic and easily verifiable factors aligns with efficient diagnostic practices in HVAC troubleshooting.