How do I perform a system test on the thermostat?
Press and hold the Menu button for 5 seconds to access the Advanced Menu, then navigate to System Test. Select the test type (heat, cool, or fan) and use the arrow buttons to activate each stage. The clock serves as a timer while stages are running.
From the official Honeywell Lyric T6 Pro Wi-Fi Smart Thermostat manual, page 17
Have a follow-up question?
Answers from the official manual.
Common questions