Error Code Heat On flashing
Compressor protection feature is engaged or startup delay protection is active — the system is waiting before restarting.
? What Causes This
Compressor was recently shut down, or AC power loss occurred; the system is protecting against damage from rapid restart.
✓ How to Fix It
Wait a few minutes for the system to safely restart. This is normal during power recovery. See page 9 for more information.
Source: page 9 of the official manual
From the manual
Affected Honeywell Products
Honeywell T6 Pro Thermostat
Thermostats
Honeywell T4 Pro Thermostat
Thermostats
Honeywell TH6220D1028 Thermostat
Thermostats
Honeywell T6 Pro Smart Thermostat
Thermostats
Honeywell TH5220D1029 Thermostat
Thermostats
Honeywell 6000 Series Programmable Thermostat
Thermostats
Honeywell T6 Thermostat
Thermostats
Honeywell T4 Thermostat
Thermostats
Honeywell Home Pro Series Thermostat
Thermostats
Honeywell TH6110D Programmable Digital Thermostat
Thermostats
Honeywell T6220D Programmable Thermostat
Thermostats
Honeywell TH5110D Home Programmable Thermostat
Thermostats
Honeywell TH3000 Programmable Thermostat
Thermostats
Honeywell T1 Pro Thermostat
Thermostats
Honeywell Focuspro TH5220D Thermostat
Thermostats
Honeywell Pro Th4210D
Thermostats