Honeywell RTH6400 Operating Manual page 23

In case of difficulty
Heating or
cooling system
does not respond
"Cool On" or
"Heat On" is
flashing
Other problems
• Press SYSTEM button to set system to Heat. Make sure the temperature
is set higher than the Inside temperature.
• Press SYSTEM button 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.
• Compressor protection feature is engaged. Wait 5 minutes for the system
to restart safely, without damage to the compressor (see page 14).
• If the above measures do not resolve the problem, check the In Case of
Difficulty section in your thermostat Installation Guide .
RTH6400 Programmable Thermostat
2 69-22EF—0