Honeywell Programmable Thermostat Owner's Manual page 46

Heating will not come one.
Cooling will not come on.
The house is too warm or too cool.
Display says HEAT ON or system
light is on, but no heat is coming
from the registers.
Check the fuse or circuit breaker and replace or reset if necessary. If
display is blank or says REPL BAT, install fresh batteries.
Check that switch on thermostat is set to HEAT or AUTO.
If temperature setting is higher than current temperature, and display
says HEAT ON, contact your heating and air conditioning contractor.
Check the fuse or circuit breaker and replace or reset if necessary. If
display is blank or says REPL BAT, install fresh batteries.
Check that switch on thermostat is set to COOL or AUTO.
The thermostat has a built-in time delay on cooling to protect the
compressor. Allow up to 10 minutes after changing the setting before
the air conditioner starts.
If temperature setting is lower than current temperature, and display
says COOL ON, contact your heating and air conditioning contractor.
Press PRESENT SETTING to check the current temperature setting.
If desired, change the time or temperature setting. See page 25.
Allow time for the furnace to heat up and the fan to come on
before checking for heat at the register.
TROUBLESHOOTING
42