Why are 'Cool On' or 'Heat On' flashing on my thermostat display?
The flashing indicates that the compressor protection feature is engaged. You should wait 5 minutes for the system to restart safely without damage to the compressor. This is a normal protective function and does not indicate a fault requiring service. (Page 13)
From the official Honeywell Honeywell Thermostat Manuals Pro Series Honeywellhome And Others manual, page 13
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