How do you test a preheat control unit?

To test a preheat control unit, first ensure that the power supply is turned off for safety. Then, use a multimeter to check for continuity in the unit's components, such as the thermostat and relays, making sure they function correctly. Next, apply power to the unit and monitor its operation to verify that it reaches the appropriate temperature settings within the specified time. Finally, check for any error codes or indicators on the control panel to confirm proper functionality.