Honeywell RTH8500 Installation Manual page 27

About your new thermostat In case of difficulty
Heating or
cooling system
does not respond
Red warning
light is on
• Press SYSTEM to set system to Heat. Make sure the temperature is set
higher than the Inside temperature.
• Press SYSTEM to set system to Cool. Make sure the temperature is set
lower than the Inside temperature.
• Check circuit breaker and reset if necessary.
• Make sure power switch at heating & cooling system is on.
• Make sure furnace door is closed securely.
• Wait 5 minutes for the system to respond.
• If thermostat is in Emergency Heat mode the red light is normal. It
shows that the thermostat is in emergency heat mode.
• If thermostat is not in Emergency Heat mode, contact a qualified
service contractor for repair.
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RTH8500