– 33 –
Fault
Code
Number
Fault Meaning
Effect on Operation
While Fault is ACTIVE
Fault Reset Time
F10
Heat pump over-temperature
fault. The temperature of the
indoor coil is over 131°F.
The outdoor fan motor is
shut down until the coil
temperature recovers.
Fault clears
once indoor coil
temperature drops
below 122°F.
F11
Inlet air temperature. Indoor air
thermistor warmer than 95°F.
Shut off compressor and
resistance heat operation
until inlet thermistor
temperature drops below
85°F.
Fault clears once air
temperature drops
below 85°F.
F12
UI board disconnected/failed.
No effect.
F13
Heater airflow fault
: The main
board detects too low of indoor
fan speed.
No resistance heat or heat
pump available.
Fault clears after
X
minutes.
F16
Make-Up Air module
communication fault.
No communication
between Zoneline and
Maku-Up air module.
F17
Outlet thermistor failure. Fault
clears when thermistor reads
value other than short circuit or
open circuit.
No resistance heating
available.
F18
Outlet temperature overheat.
The outgoing air is too hot. Fault
clears when air temperature
drops below threshold.
No resistance heating
available.
F19
Outlet temperature overheat.
The outgoing air is too hot.
No resistance heating
available.
F23
Make-up Air Module Fault
Shuts Down MUAM,
including MUAM
compressor
F24
Make-up Air Module Vent Door
Fault
This is set if the vent door
state change validation
fails.
No effect
F25
Abnormal Defrost Fault (heat
pump models only). Set when
five consecutive defrost cycles
failed to warm outdoor coil above
68°F.
Locks out heat pump,
locks out defrost.
Will self-clear after 4.5
days.
F26
Air Conditioning Lockout Fault
(heat pump models only).
Sets when outdoor ambient
temperature drops below 35°F.
Locks out compressor
cooling operation.
Will self-clear after
Outdoor Ambient
temperature rises
above 40°F.
