Honeywell RTH8500 Series - Troubleshooting; Display is Blank; Cannot Change System Setting to Cool; Fan Not Turning On When Heat is Required

33-00133ES—01 26
If you have difficulty with your thermostat, please try the following suggestions.
Most problems can be corrected quickly and easily.
Display is
blank
• Check circuit breaker and reset if necessary.
• Make sure power switch at heating and cooling system is on.
• Make sure furnace door is closed securely.
• Make sure C wire is connected (see page 6).
Cannot change
system setting
to Cool
• Check Function 0170: System Type to make sure it is set to match your
heating and cooling equipment (see page 22).
Fan does
not turn on
when heat is
required
• Check Function 0180: Heating Fan Control to make sure it is set to match
your heating equipment (see page 22).
“Wait” appears
on the screen
• Compressor protection feature is engaged. Wait 5 minutes for the system to
restart safely, without damage to the compressor.
Heat pump
issues cool air
in heat mode,
or warm air in
cool mode
• Check Function 0190: Heat Pump Changeover Valve to make sure it is
properly configured for your system (see page 22).
Button on
lower right of
screen is blank
• This button will remain blank unless the furnace filter change reminder is
activated (see page 17).
Red light is on • 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.
Heating or
cooling system
does not
respond
• 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.
• If “Wait” is displayed, the compressor protection timer is on. Wait 5 minutes
for the system to restart safely, without damaging the compressor (see page
19).
Heating system
is running in
cool mode
• Check Function 0170: System Type to make sure it is set to match your
heating and cooling equipment (see page 22).
Troubleshooting