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18-HD64D1-1 17
Section 7. Troubleshooting
Symptom Possible Causes Action
Thermostat displays an alert
code on the screen.
Alert Code is present. Refer to the Alert Code Addendum. Check the
Alert icons in the diagnostic screen.
Display will not come on Loss of 24VAC between R & B at the thermo-
stat.
1) Check wiring between R & B to see if R & D, or
B & D have been reversed.
2) Check transformer for 24VAC output.
3) Check for broken or shorted thermostat wire.
Indoor temperature display is
incorrect.
Indoor temperature display needs calibration. Calibrate temperature sensor from thermostat
menu.
Indoor humidity display is incor-
rect.
Indoor humidity display needs calibration. Calibrate humidity sensor from the thermostat
menu.
Room temperature overshoots
when the Heat/Cool setting is
changed more than 2°.
1) Oversized heating/cooling equipment under
current conditions. Control cannot respond fast
enough to prevent overshooting.
2) Improper location of thermostat.
3) Aggressive recovery is activated.
1) Compare heat load calculation to equipment
chosen.
2) Relocate thermostat (or use remote sensor) if
thermostat is in “dead” spot (poor or no air circula-
tion).
3) Deactivate aggressive recovery.
Heating will not come on. 1) System mode is not set to heat/Auto or set-
point is set too low.
2) Minimum off time delay is being enforced.
3) Heating system may require service.
1) Set mode to heat and raise the setpoint above
the room temperature.
2) Wait for 5 minutes and recheck heating equip-
ment.
3) Check/repair system.
Cooling will not come on. 1) System mode is not set to cool/Auto or the
setpoint is too high.
2) Minimum off time delay is being enforced.
3) Cooling system may require service.
1) Set mode to cool and lower the setpoint below
the room temperature.
2) Wait for 5 minutes and recheck cooling equip-
ment.
3) Check/repair system.
Heating or Cooling is displayed,
but no warm or cool air is coming
from the registers.
1) There is a fan delay as the heating or cooling
equipment turns on.
2) Equipment is not working properly.
1) Wait a minute for blower delays and recheck
registers.
2) Check/repair system.
Fan runs all the time 1) Fan mode is set to On, Circulate or Clean
mode
2) There is a failure in the indoor unit
1) Check thermostat settings to see if fan is set to
On, Circulate or Clean mode.
2) Check indoor unit for failures (such as tripped
heating limit).
Fan is set to ON but not running. 1) Humidity control is engaged.
2) Blower motor is not functioning.
1) If indoor humidity is higher than desired set-
point, the blower will cycle off with the equipment.
2) Check/repair system.
Cooling or Heating cycles too
fast or too slow (narrow or wide
temperature swings).
1) Check the location of the thermostat for
drafts.
2) Cycles per hour or aggressive recovery is
improperly set.
1) Seal all air leaks behind thermostat. Relocate
thermostat or apply remote indoor temperature
sensor.
2) Adjust cycle rates and aggressive recovery
features in the advanced installer set up.
Heat pump is not turning on; only
furnace or electric heat strips are
running.
1) Outdoor temperature is below compressor
lockout temperature setting.
2) Compressor heating lockout is enabled and
outdoor temp sensor is out of calibration or
failed.
1) Check/repair outdoor sensor or wiring.
2) Adjust the compressor lockout temperature
setting if desired.
Cannot change system mode to
desired setting.
Equipment is not configured properly. Check the standard installer set up screen to
ensure equipment is properly configured.
Screen does not respond prop-
erly to a button press
Screen is out of calibration Remove thermostat from sub base and reset.
Follow the calibration instructions when the ther-
mostat reboots.
“No System Found” displayed on
the thermostat
Internal error Reboot the thermostat via onscreen button.
Slow or no response to any but-
ton presses
Internal error Remove the thermostat from the sub base and
reset.