ACONT900AC43UA
Pub. No. 11-HD04D1-2
21
69-2080—05
Table 7. Troubleshooting Information
Symptom
Possible Cause
Action
Red service LED is illuminated
and the display alternates
between Home screen and Alert
Code screen.
Alert Code present
Refer to the Alert Code Addendum (form
18-HD32D2-1/69-2009).
Display will not come on.
1. Blown fuse or tripped circuit
breaker.
2. Indoor unit power switch OFF.
3. Indoor unit blower
compartment door or panel loose
or not properly installed.
4. Wire broken/shorted; or R and
D or B and D are reversed.
1. Replace fuse or reset breaker.
2. Turn power switch to ON.
3. Replace door panel in proper position
to engage safety interlock or door switch
on furnace.
4. Check R, B, D wiring.
Indoor temperature display is
incorrect.
Temperature display needs
calibration.
Calibrate Sensor - ISU 0700
Indoor humidity display is
incorrect.
Indoor humidity display needs
calibration.
Calibrate Sensor - ISU 0701
Outdoor temperature display
shows “--” or the outdoor
temperature is not displayed.
1. Outdoor temperature sensor
open, shorted, not reporting, or
not installed.
2. Outdoor sensor field wiring
open or shorted.
1. Replace/Install outdoor sensor.
2. Check/repair outdoor sensor field
wiring.
Indoor temperature display shows
“--”.
Indoor temperature sensor open
or shorted.
Replace control.
Temperature setting will not
change (e.g. Cannot increase
heating setpoint or reduce cooling
setpoint).
1. Upper and/or lower
temperature limits were reached.
2. Keys are fully locked. “Screen
Locked” is displayed on LCD.
1. Check the temperature setpoints:
Heating limits (ISU 0600) are 40°F - 90°F
(4.4°C - 32.2°C).
Cooling limits (ISU 0610) are 60°F - 99°F
(15.5°C - 32.2°C).
2. Unlock keypad - ISU 0670.
Room temperature overshoots
when the Heat/ Cool setting is
changed more than 2 degrees.
1. Oversized heating/cooling
equipment under current
conditions. Control cannot
respond fast enough to prevent
overshooting.
2. Improper location of comfort
control.
1. Set Control Response rate to
“Aggressive” - ISU 0680, 0690
2. Select a location that prevents the
Comfort Control from being directly
exposed to air currents from supply
registers.
Heating will not come on.
1. System Mode not set to Heat.
2. Minimum off time delay being
enforced.
3. Loose connection to control or
system.
4. Heating system may need
service.
1. Set Mode to heat and raise the
setpoint above room temperature.
2. If heating does not come on within 5
minutes, checking heating equipment.
3. Check/repair connections.
4. Repair system.
Cooing will not come on.
1. System Mode not set to Cool.
2. Minimum off time delay being
enforced.
3. Loose connection to control or
system.
4. Cooling system may need
service.
1. Set Mode to cool and lower the
setpoint above room temperature.
2. If cooling does not come on within 15
minutes, checking cooling equipment.
3. Check/repair connections.
4. Repair system.
Heat ON or Cool ON is displayed,
but no warm air or cool air is
coming from the registers.
1. The heating equipment turns
on the fan when the furnace has
warmed up.
2. Heating or cooling equipment
is not operating.
1. Wait one minute after Heat ON is
displayed and then check the registers.
2. Check Heating and/or Cooling
equipment.
Control does not respond to
keypad screen presses.
1. Keys are fully locked. “Screen
Locked” is displayed on LCD.
2. Keypad failure.
1. Unlock keypad - ISU 0670.
2. Replace control.
Fan does not operate properly in
heat or cool mode.
1. Heating or cooling equipment
inoperative.
1. Repair system.
