Temperzone Air Conditioner Fault Codes

What does your Temperzone fault code mean?

Pick the code showing on your remote, wall controller or indoor unit and see what it means, what commonly causes it, and what is safe to check yourself. This page covers 89 Temperzone fault codes for units sold in Australia, compiled from official Australian manufacturer and distributor documentation, the same references our own technicians carry.

Heads up: Temperzone uses the same code with different meanings on different product ranges, so check the model range shown next to the code.

Every Temperzone fault code at a glance

Some models show faults as a flashing-light pattern instead of a code; documented lamp patterns are listed alongside their codes.

Code	What it means	Severity
1 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 1	Room temperature sensor 1 has failed.	Minor fault
10 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 10	High refrigerant pressure protection has tripped.	Fault – service needed
11 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 11	Room temperature sensor 5 (at wallpad B) has failed.	Minor fault
12 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 12	Room temperature sensor 6 (at wallpad A) has failed.	Minor fault
13 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 13	All room temperature sensors have failed.	Fault – service needed
14 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 14	The condensate float switch has tripped, usually meaning the drain is blocked and the safety tray is filling.	Fault – service needed
15 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 15	Low safety thermostat 1 has tripped or failed.	Minor fault
16 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 16	Communication has failed between the SAT-2 and the unit.	Fault – service needed
17 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 17	The hydronic pump switch has tripped or failed (water source units).	Fault – service needed
18 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 18	The system has detected insufficient refrigerant on circuit 2 (dual circuit units).	Fault – service needed
19 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 19	Compressor 2 overload protection has tripped (dual circuit units).	Fault – service needed
2 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 2	Room temperature sensor 2 or low safety thermostat sensor 2 has failed.	Minor fault
20 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 20	Low safety thermostat 2 has tripped or failed (dual circuit units).	Minor fault
21 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 21	Discharge sensor 1 has failed.	Minor fault
22 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 22	Discharge sensor 2 has failed.	Minor fault
23 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 23	Discharge temperature 1 protection has tripped (compressor running too hot).	Fault – service needed
24 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 24	Discharge temperature 2 protection has tripped (compressor running too hot).	Fault – service needed
3 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 3	Room temperature sensor 3 or indoor coil sensor 2 has failed.	Minor fault
4 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 4	Room temperature sensor 4 or discharge sensor 1 has failed.	Minor fault
5 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 5	Indoor coil sensor 1 has failed.	Minor fault
6 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 6	Low safety thermostat (LST) sensor 1 has failed.	Minor fault
7 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 7	The system has detected insufficient refrigerant on circuit 1.	Fault – service needed
8 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 8	Compressor 1 overload protection has tripped.	Fault – service needed
9 (SAT-2 wall thermostat (older LCD wall controller on Temperzone ducted and packaged systems); the number shows next to the ERR symbol and the backlight turns red) also shown as ERR 9	Low refrigerant pressure protection has tripped.	Fault – service needed
A1 (SAT-3 wall thermostat (wall controller on many Temperzone ducted systems) with the six zone controller; A1 on its own is a zone fault, A1 paired with A4 to A8 relays a unit fault; A1 A2, A1 A3, A2 A3 and A1 A2 A3 can also mean a combination of the three zone faults)	Zone damper calibration has not been completed.	Minor fault
A2 (SAT-3 wall thermostat (wall controller on many Temperzone ducted systems) with the six zone controller; A2 on its own is a zone fault, A2 paired with A4 to A8 relays a unit fault; A1 A2, A1 A3, A2 A3 and A1 A2 A3 can also mean a combination of the three zone faults)	Zone damper calibration has failed.	Minor fault
A3 (SAT-3 wall thermostat (wall controller on many Temperzone ducted systems) with the six zone controller; A3 on its own is a zone fault, A3 paired with A4 to A8 relays a unit fault; A1 A2, A1 A3, A2 A3 and A1 A2 A3 can also mean a combination of the three zone faults)	Communication between the zone controller and the unit controller has been lost.	Fault – service needed
A4 (SAT-3 wall thermostat (wall controller on many Temperzone ducted systems); A4 on its own means lock out, A4 paired with another A number relays a unit fault)	The unit has locked itself out after three protection trips in a row; the display on the unit controller shows the cause.	Fault – service needed
CRH (Water cooled MWC, MWH and MWR-L models fitted with the UC8 controller)	High compression ratio protection has activated because the pressure difference across the compressor is too large.	Fault – service needed
CRL (Water cooled MWC, MWH and MWR-L models fitted with the UC8 controller)	Low compression ratio protection has activated, usually because the compressor is not starting or not pumping.	Fault – service needed
F10 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A7 on a SAT-3 wall controller) also shown as A3 A7	The unit controller has lost contact with the outdoor fan speed controller, so the outdoor fan is not being driven properly.	Fault – service needed
F100 (Temperzone units with a Carel Power+ inverter compressor drive on the UC8 controller (including water cooled MW models); F100 on its own means lost communications, F100 plus a number is the drive alarm code) also shown as F101 to F129, F197 to F199	The inverter compressor drive is reporting a fault; the number after F100 identifies the specific drive alarm (for example F103 mains voltage too high, F104 mains voltage too low, F105 drive too hot).	Fault – service needed
F11 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A7 on a SAT-3 wall controller) also shown as A3 A7	The unit controller has lost contact with the indoor fan speed controller, so the indoor fan is not being driven properly.	Fault – service needed
F12 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; on the UC8 this is the low pressure transducer, on the older UC7 it is the high pressure transducer; shows as A3 A8 on a SAT-3 wall controller) also shown as A3 A8	A refrigerant pressure sensor (transducer) has failed or is giving readings outside its normal range.	Fault – service needed
F13 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; on the UC8 this is the high pressure transducer, on the older UC7 it is the low pressure transducer; shows as A3 A8 on a SAT-3 wall controller) also shown as A3 A8	A refrigerant pressure sensor (transducer) has failed or is giving readings outside its normal range.	Fault – service needed
F14 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A8 on a SAT-3 wall controller) also shown as A3 A8	The suction line temperature sensor has failed (open or short circuit).	Minor fault
F15 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A8 on a SAT-3 wall controller) also shown as A3 A8	The compressor discharge line temperature sensor has failed (open or short circuit).	Minor fault
F16 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A8 on a SAT-3 wall controller) also shown as A3 A8	The outdoor coil de-ice temperature sensor has failed, so the unit cannot manage its defrost cycles properly.	Minor fault
F17 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; on water cooled MW models this is the leaving water temperature sensor; shows as A3 A8 on a SAT-3 wall controller) also shown as A3 A8	A unit temperature sensor has failed (open or short circuit): the outdoor coil sensor on air based units, or the leaving water sensor on water cooled MW models.	Minor fault
F18 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; on water cooled MW models this is the entering water temperature sensor; shows as A3 A8 on a SAT-3 wall controller) also shown as A3 A8	A unit temperature sensor has failed (open or short circuit): the indoor coil sensor on air based units, or the entering water sensor on water cooled MW models.	Minor fault
F19 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A8 on a SAT-3 wall controller) also shown as A3 A8	The outdoor ambient temperature sensor has failed (open or short circuit).	Minor fault
F20 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A2 A8 on a SAT-3 wall controller) also shown as A1 A2 A8	The controller cannot work out the refrigerant superheat because one of its sensors or transducers is missing or faulty.	Minor fault
F21 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit)	The unit controller has lost communication with the wall thermostat, so the system cannot respond to the wall control.	Fault – service needed
F22 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A2 A4 on a SAT-3 wall controller) also shown as A2 A4	The unit has lost communication with the master unit or building management system (BMS).	Fault – service needed
F23 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; mainly multi unit (master and slave) installations; shows as A2 A5 on a SAT-3 wall controller) also shown as A2 A5	Communication with slave unit 1 has been lost.	Fault – service needed
F24 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; mainly multi unit (master and slave) installations; shows as A2 A6 on a SAT-3 wall controller) also shown as A2 A6	Communication with slave unit 2 has been lost.	Fault – service needed
F25 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; mainly multi unit (master and slave) installations; shows as A2 A7 on a SAT-3 wall controller) also shown as A2 A7	Communication with slave unit 3 has been lost.	Fault – service needed
F26 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); on the UC8 this is the controller being unable to read its DIP switches, on the older UC7 (and in the water cooled MW document) it means the DIP switches are set to an invalid combination; shows as A1 A2 A6 on a SAT-3 wall controller) also shown as A1 A2 A6	A DIP switch configuration fault on the unit controller: the switches are set to an invalid combination, or the controller cannot read them.	Fault – service needed
F27 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A2 A6 on a SAT-3 wall controller) also shown as A1 A2 A6	An invalid fan configuration has been selected on the controller DIP switches.	Fault – service needed
F28 (UC8: missing outdoor coil de-ice sensor or heating requested on a cooling only unit. UC7: invalid economiser selection. Both are configuration faults)	A configuration fault: the controller is being asked to do something the unit is not set up for.	Fault – service needed
F29 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A2 A6 on a SAT-3 wall controller) also shown as A1 A2 A6	The controller circuit board itself is running too hot.	Fault – service needed
F30 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A2 A6 on a SAT-3 wall controller) also shown as A1 A2 A6	The mains supply voltage to the unit is outside the safe operating range.	Fault – service needed
F31 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; multi unit (master and slave) installations; shows as A2 A3 A4 on a SAT-3 wall controller) also shown as A2 A3 A4	A slave unit in a multi unit system is reporting its own fault.	Fault – service needed
F32 (UC8: internal communications problem on the controller board. UC7: 0-10V input board fault. Shows as A1 A2 A6 on a SAT-3 wall controller) also shown as A1 A2 A6	An internal fault on the unit controller circuit board.	Fault – service needed
F33 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; same condition as the Hi-dSH message; shows as A3 A5 on a SAT-3 wall controller) also shown as Hi-DSH, A3 A5	High discharge superheat protection, which usually means the system is running low on refrigerant.	Fault – service needed
F34 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A4 A8 on a SAT-3 wall controller) also shown as A4 A8	The controller is getting implausible readings from the refrigerant pressure transducers (pressures not equalising).	Fault – service needed
F35 (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A2 A3 on a SAT-3 wall controller (note the SAT-3 also uses A2 A3 for a zone damper fault combination)) also shown as A2 A3	The reverse cycle valve has failed to switch between heating and cooling.	Fault – service needed
F36 (Units controlled by the TZT-100 wall thermostat with a UC7 or UC8 controller; shows as A1 A2 on a SAT-3 wall controller (note the SAT-3 also uses A1 A2 for the combination of both zone damper calibration faults)) also shown as A1 A2	The DIP switches inside the TZT-100 wall thermostat are set incorrectly for this unit.	Fault – service needed
F37 (Ducted split systems with a UC8 outdoor controller and an IUC indoor unit controller (OSA/ISD ranges); shows as A2 A8 on a SAT-3 wall controller) also shown as A2 A8	The outdoor unit has lost communication with the indoor unit.	Fault – service needed
F38 (Ducted split systems with a UC8 outdoor controller and an IUC indoor unit controller (OSA/ISD ranges); shows as A7 A8 on a SAT-3 wall controller) also shown as A7 A8	The indoor unit controller is reporting a fault of its own.	Fault – service needed
F39 (Temperzone units with a variable speed (inverter) compressor on the UC8 controller; shows as A6 A7 on a SAT-3 wall controller) also shown as A6 A7	The variable speed compressor drive (inverter) is reporting a fault.	Fault – service needed
F40 (Units fitted with the UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A4 A5 on a SAT-3 wall controller) also shown as A4 A5	The compression ratio is too high, meaning the compressor is working much harder than it should.	Fault – service needed
F41 (Units fitted with the UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A4 A6 on a SAT-3 wall controller) also shown as A4 A6	The compression ratio is too low, which usually means the system is undercharged with refrigerant.	Fault – service needed
F42 (Units fitted with the UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A4 A7 on a SAT-3 wall controller) also shown as A4 A7	The evaporating temperature or pressure is too high for safe compressor operation.	Fault – service needed
F43 (Units fitted with the UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A4 A8 on a SAT-3 wall controller) also shown as A4 A8	The condensing temperature or pressure is too low for safe compressor operation.	Fault – service needed
F44 (Water cooled MWC, MWH and MWR-L models fitted with the UC8 controller)	An invalid expansion valve operating mode has been selected on the controller DIP switches.	Fault – service needed
F45 (Water cooled MWC, MWH and MWR-L models fitted with the UC8 controller; listed by Temperzone as not in use in current software)	Low evaporating temperature fault (reserved code, listed by Temperzone as not in use).	Normal operation
F46 (Water cooled MWC, MWH and MWR-L models fitted with the UC8 controller)	The controller has lost communication with the six temperature sensor board (6TB).	Fault – service needed
FLOOd (Hydronic Temperzone units with a condensate sump on the UC8 controller; shows as A5 A7 on a SAT-3 wall controller) also shown as Flood, A5 A7	The condensate sump flooding protection has activated because condensate water is not draining away.	Fault – service needed
FROSt (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A6 on a SAT-3 wall controller) also shown as Frost, A1 A6	Indoor coil frost protection has activated because the indoor coil is getting cold enough to ice up while cooling.	Minor fault
HI-SL (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A8 on a SAT-3 wall controller) also shown as Hi-SL, A1 A8	High suction line temperature protection has activated to stop the compressor motor from overheating.	Fault – service needed
HI-t (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A7 on a SAT-3 wall controller) also shown as Hi-t, A1 A7	High temperature protection has activated because the compressor discharge line is running too hot.	Fault – service needed
HOLd (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit)	Not a fault: the compressor is being held on or off by a safety timer and will resume by itself.	Normal operation
HP (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A4 on a SAT-3 wall controller) also shown as A1 A4	High pressure protection has activated because the refrigerant pressure has climbed too high.	Fault – service needed
Hi-dSH (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; also reported as fault F33; shows as A3 A5 on a SAT-3 wall controller) also shown as HI-dSH, A3 A5	High discharge superheat protection has activated, which usually means the system is running low on refrigerant.	Fault – service needed
LO-t (Hydronic (water source) Temperzone units and chillers on the UC8 controller (the older UC7 has the same freeze protection function but its guide does not document this display message); MW models show FREEZE; shows as A5 A6 on a SAT-3 wall controller) also shown as Lo-t, FREEZE, A5 A6	Water freeze protection has activated to stop the circulating water from freezing.	Fault – service needed
LP (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A5 on a SAT-3 wall controller) also shown as A1 A5	Low pressure protection has activated because the refrigerant pressure has dropped too low.	Fault – service needed
Lo-dSH (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A4 on a SAT-3 wall controller) also shown as Lo-DSH, A3 A4	Low discharge superheat protection has activated because liquid refrigerant may be flooding back to the compressor.	Fault – service needed
OL (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A6 on a SAT-3 wall controller) also shown as A3 A6	Overload protection has activated because the compressor or a fan motor has drawn too much current or overheated.	Fault – service needed
c (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit)	Not a fault: the unit is in commissioning mode, which expires automatically after 30 minutes.	Normal operation
dE-ICE (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit)	Not a fault: the unit is de-icing (defrosting) the outdoor coil, which is normal in cold weather while heating.	Normal operation
dELAY (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit)	Not a fault: the unit is waiting out a short random start delay after power on.	Normal operation
diFF-P (Water cooled MWC, MWH and MWR-L models fitted with the UC8 controller)	The pressure difference across the system is too high for the inverter compressor to start.	Fault – service needed
dr (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit)	Not a fault: a DRED energy demand restriction from your electricity provider is temporarily limiting the unit.	Normal operation
nO-FLO (Hydronic (water source) Temperzone units and chillers on the UC8 controller; shows as A5 A8 on a SAT-3 wall controller) also shown as No-Flo, A5 A8	The circulating water flow protection has activated because the unit cannot detect enough water flow.	Fault – service needed
t (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit)	Not a fault: the unit is in test mode, which expires automatically after about 1 minute.	Normal operation
t1 (SAT-3 wall thermostat (wall controller on many Temperzone ducted systems))	The temperature sensor inside the SAT-3 wall controller has failed.	Minor fault
t2 (SAT-3 wall thermostat (wall controller on many Temperzone ducted systems))	The external (remote room) temperature sensor connected to the SAT-3 has failed.	Minor fault
t3 (SAT-3 wall thermostat (wall controller on many Temperzone ducted systems))	The SAT-3 wall controller has lost communication with the zone controller or the unit controller.	Fault – service needed

The most serious Temperzone fault codes explained

What does Temperzone fault code LP mean? (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A5 on a SAT-3 wall controller)

Low pressure protection has activated because the refrigerant pressure has dropped too low.

Likely causes:

• Refrigerant leak (low refrigerant charge)
• Electronic expansion valve stuck closed or disconnected
• Faulty pressure transducer or its cable
• Service valve left closed after installation or service

Safe checks before you call:

• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)
• If the fault returns, leave the system off and book a service call

What does Temperzone fault code HP mean? (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A4 on a SAT-3 wall controller)

High pressure protection has activated because the refrigerant pressure has climbed too high.

Likely causes:

• Outdoor fan not running (cooling) or indoor fan not running (heating)
• Outdoor coil blocked by leaves, dirt or debris
• System overcharged with refrigerant
• Expansion valve stuck closed
• Faulty pressure transducer, cable or HP switch

Safe checks before you call:

• Check nothing is piled against the outdoor unit and clear away any leaves or debris around it
• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)

What does Temperzone fault code HI-t mean? (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A7 on a SAT-3 wall controller)

High temperature protection has activated because the compressor discharge line is running too hot.

Likely causes:

• Insufficient refrigerant (leak)
• Faulty discharge line temperature sensor
• Expansion valve problem

Safe checks before you call:

• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)
• If the code returns, stop using the system and book a service call

What does Temperzone fault code HI-SL mean? (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A1 A8 on a SAT-3 wall controller)

High suction line temperature protection has activated to stop the compressor motor from overheating.

Likely causes:

• Insufficient refrigerant (leak)
• Very high room temperature while cooling (for example first start on a very hot day)
• Very high outdoor temperature while heating
• Faulty suction line temperature sensor

Safe checks before you call:

• Let the system rest for 10 minutes, then restart it at a milder set temperature
• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on

What does Temperzone fault code Lo-dSH mean? (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A4 on a SAT-3 wall controller)

Low discharge superheat protection has activated because liquid refrigerant may be flooding back to the compressor.

Likely causes:

• System overcharged with refrigerant
• Discharge line temperature sensor loose or faulty
• Wrong expansion valve configuration set after service work

Safe checks before you call:

• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)

What does Temperzone fault code Hi-dSH mean? (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; also reported as fault F33; shows as A3 A5 on a SAT-3 wall controller)

High discharge superheat protection has activated, which usually means the system is running low on refrigerant.

Likely causes:

• Loss of refrigerant through a leak
• Faulty discharge line pressure transducer
• Wrong expansion valve configuration set after service work

Safe checks before you call:

• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)
• If the code returns, book a service call as running low on refrigerant can damage the compressor

What does Temperzone fault code OL mean? (Units fitted with the UC7 or UC8 unit controller (OSA/ISD ducted splits, OPA packaged units and other Temperzone ranges); the code shows on the controller display inside the unit; shows as A3 A6 on a SAT-3 wall controller)

Overload protection has activated because the compressor or a fan motor has drawn too much current or overheated.

Likely causes:

• Compressor overheated (often after running hard on a hot day)
• Indoor or outdoor fan overloaded or airflow obstructed
• Faulty wiring or connection to the overload input

Safe checks before you call:

• Check nothing is blocking airflow at the outdoor unit or the return air grille
• Let the system rest for 30 minutes, then turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on

What does Temperzone fault code LO-t mean? (Hydronic (water source) Temperzone units and chillers on the UC8 controller (the older UC7 has the same freeze protection function but its guide does not document this display message); MW models show FREEZE; shows as A5 A6 on a SAT-3 wall controller)

Water freeze protection has activated to stop the circulating water from freezing.

Likely causes:

• Insufficient water flow (pump or closed valve)
• Supply water temperature too low
• Low refrigerant charge
• Water temperature sensor out of position (MW models)

Safe checks before you call:

• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)

What does Temperzone fault code nO-FLO mean? (Hydronic (water source) Temperzone units and chillers on the UC8 controller; shows as A5 A8 on a SAT-3 wall controller)

The circulating water flow protection has activated because the unit cannot detect enough water flow.

Likely causes:

• Circulating water pump not running
• Closed water valve
• Faulty water flow switch

Safe checks before you call:

• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)

What does Temperzone fault code FLOOd mean? (Hydronic Temperzone units with a condensate sump on the UC8 controller; shows as A5 A7 on a SAT-3 wall controller)

The condensate sump flooding protection has activated because condensate water is not draining away.

Likely causes:

• Blocked condensate drain pipe
• Drain pipe with too little fall, or no U-trap fitted
• Faulty condensate float switch or pump

Safe checks before you call:

• If you can see the drain outlet, check it is not visibly blocked by dirt or debris
• Avoid running cooling until the drain is cleared, then book a service call

What does Temperzone fault code CRL mean? (Water cooled MWC, MWH and MWR-L models fitted with the UC8 controller)

Low compression ratio protection has activated, usually because the compressor is not starting or not pumping.

Likely causes:

• Compressor fails to start
• Compressor contactor or wiring fault

Safe checks before you call:

• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)

What does Temperzone fault code CRH mean? (Water cooled MWC, MWH and MWR-L models fitted with the UC8 controller)

High compression ratio protection has activated because the pressure difference across the compressor is too large.

Likely causes:

• Faulty pressure transducer
• Expansion valve malfunctioning or disconnected
• Indoor fan or fan controller malfunction

Safe checks before you call:

• Turn the system off at the isolator or circuit breaker, wait 5 minutes, then turn it back on (this also clears a lock-out)

Fault confirmed? Here is what to do next

A fault code is the starting point, not the fix. Start here:

• Air conditioner repairs – how we diagnose and fix Temperzone faults across Adelaide. Our fault find covers the full diagnosis, and it is on us if you go ahead with the repair.
• Repair or replace calculator – whether fixing your current system is the smarter money.
• Service and maintenance – regular servicing prevents most of the faults on this page.
• Air conditioner fault code lookup – all 15 brands in one place.
• All calculators and tools

Call us on 08 8296 7888 or book online and we will call or text you back ASAP.

Sources for this page

Every Temperzone code above is checked against these Australian documents. Open them yourself to verify anything on this page:

• UC8 Fault and Display Messages A t A 0615 (PDF) (temperzone.com)
• UC8 Fault and Display Messages Hydronics (PDF) (temperzone.com)
• UC8 Troubleshooting Guide v2 0715 (PDF) (temperzone.com)
• UC7TroubleshootingGuide 1012 3 (PDF) (temperzone.com)
• temperzone air conditioner error codes brisbane (iceblast.com.au)
• SAT 3DisplayFaultCodes 1115 (PDF) (usp.temperzone.com)
• UC8 Fault Codes MWHMWRMWC L models v1 extract (PDF) (usp.temperzone.com)
• Temperzone SAT 2 User Manual (PDF) (penrithair.com.au)

Temperzone fault code FAQs

Written by Oliver Hastings, T&K Airpower. Last updated 01/08/2026. Compiled from Australian sources including temperzone.com, iceblast.com.au, usp.temperzone.com, penrithair.com.au, so you can check every code against the official documentation. Fault code meanings vary between model series and controllers, so treat this page as reference only and never remove panels or work on the refrigeration or electrical parts of the system yourself.