Installation Guide
40
18-HD72D1-6
9. Troubleshooting
SYMPTOM
POSSIBLE CAUSES
ACTION
Control displays an alert code on
the screen.
A critical or major alert is present.
Navigate to the Diagnostic screen on the 824 Control for a
Problem Description and Possible Cause.
Display will not come on
Loss of 24VAC between R & B at the Control.
1) Check R & B wiring.
2) Check transformer for 24VAC output.
3) Check for broken or shorted thermostat wire.
Indoor temperature display is
incorrect.
1) Indoor temperature display needs calibration.
2) Heat from touch screen is being trapped within
the thermostat body. See section 4.1 for mounting
location guidelines.
1) Calibrate temperature sensor from Sensor Settings or
use a remote temperature sensor
2) Move Control away from competing air stream or use a
remote indoor sensor.
Indoor humidity display is incorrect. Indoor humidity display needs calibration.
Calibrate humidity sensor from the Sensor Settings.
Heating will not come on.
1) System mode is not set to Heat/Auto or setpoint
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 equipment.
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 equipment.
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) Field wiring issue
3) There is a failure in the indoor unit
1) Check Control settings to see if fan is set to On,
Circulate or Clean mode.
2) Check field wiring
3) Check indoor unit for failures (such as tripped heating
limit).
“+” symbol appears on Home
Screen beneath Indoor
Temperature readout
Both compressor heat and indoor heat are being
called simultaneously
No action required, symbol is for informational purposes
only
Fan is set to ON but not running.
1) Humidity Control is engaged.
2) Field wiring issue
3) Blower motor is not functioning.
1) If indoor humidity is higher than desired setpoint, the
blower will cycle off with the equipment. A humidity icon
will be displayed on the Fan Mode button when the blower
operation is being inhibited due to high humidity.
2) Check field wiring
3) Check/repair system.
Cooling or Heating cycles too
fast or too slow (narrow or wide
temperature swings).
1) Check the location of the Control for drafts.
2) Cycles per hour is improperly set.
1) Seal air leaks behind Control. Relocate Control or apply
remote indoor temperature sensor.
2) Adjust cycle rates in the Advanced Installer Setup.
Heat pump is not turning on; only
furnace or electric heat strips are
running.
1) Outdoor temperature is below compressor
lockout temperature setting.
2) System mode is set to Emergency Heat.
3) Outdoor Unit may require service.
1) Adjust the compressor lockout temperature setting if
desired.
2) Check/repair outdoor temperature sensor or wiring.
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 properly
to a button press
1) Screen is out of calibration.
2) Internal Control fault
1) Remove Control from sub base and reset. Follow the
calibration instructions when the Control reboots.
2) Reset/Cycle power to Control by removing it from the
subbase, waiting 10 seconds and replacing.
