Why does the display keep showing 'Cool On' or 'Heat On' flashing?
The compressor protection feature is engaged. This happens to prevent equipment damage when the compressor is restarted too soon after shutdown. You need to wait 5 minutes for the system to restart safely before the compressor turns back on.
From the official Honeywell T4 Pro Programmable Thermostat (TH4110U2005/U) manual, page 8
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