How can a technician check the calibration of an adjustable close-on-fall thermostat?

A technician can check the calibration of an adjustable close-on-fall thermostat by manually rotating the shaft and comparing it to an accurate outdoor temperature. This method allows the technician to simulate the temperature conditions that the thermostat is designed to respond to. By adjusting the thermostat and observing whether it activates or deactivates at the expected setpoint temperature, the technician can assess if the thermostat is responding correctly according to its calibration.

This hands-on approach is more informative than simply replacing the thermostat, as it verifies the operational characteristics of the existing unit. Checking voltage supply or testing resistance across the terminals can provide useful information about the system's electrical performance, but it does not directly address the calibration of the thermostat itself.