Perth's Temperzone fault code lookup
Temperzone fault codes decoded
155 codes covered — what each one means, the likely cause, and whether it's worth trying something yourself before booking. Compiled from Temperzone documentation.
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Temperzone reports faults at two levels. The SAT-3 wall controller — the one you can actually see — shows short trouble codes like A1 A4, which summarise what the outdoor controller found. The UC8 or UC7 controller inside the outdoor unit holds the detail: F-numbers and word codes such as HP, LP and FROSt. Both layers are mapped below, so a SAT-3 code tells you what's really going on.
Before you scroll: exact meanings can vary between model series — treat this as a well-informed starting point, not a service manual for your specific unit. And if a code appears alongside burning smells, breaker trips or water pouring from the unit, skip the table: switch off and call 0434 951 341.
How to find your Temperzone fault code
1
What you can see: the SAT-3 wall controller
- 1 The SAT-3 is the controller most Temperzone homeowners have. It shows short trouble codes such as A1 A4 rather than the full fault number.
- 2 These are a summary layer: each SAT-3 code maps to one or more underlying UC8 controller faults (A1 A4 is a high-pressure trip, A3 A7 is a fan fault, and so on).
- 3 A4 shown on its own means the unit is locked out — the outdoor controller has tripped the safety and won't restart without attention.
2
The detail: UC8 / UC7 outdoor controller
- 1 The outdoor controller shows the full picture — either an F-number (F12, F26…) or a word code such as HP, LP, FROSt or Hi-dSH.
- 2 Word codes are protection trips: the system stopped itself for a reason it can name.
- 3 This controller is inside the outdoor unit, so reading it is a technician's job — but knowing your SAT-3 code tells them most of what they need before arriving.
Worth knowing: Temperzone equipment reports at two levels: the SAT-3 wall controller shows short summary codes to the homeowner, while the UC8/UC7 outdoor controller holds the detailed F-numbers and word codes. Meanings also differ between the UC8 and older UC7 controllers — F12 is the low-pressure transducer on a UC8 but the high-pressure transducer on a UC7 — so identify your controller before looking a number up. Several displays that look alarming (diFF-P among them) are normal hold messages rather than faults.
Temperzone fault code tables
Try this first safe check before calling anyone Book a service needs a technician Switch off & call stop running the system
What a homeowner can actually see: SAT-3 wall controller trouble codes (bottom-right 2 digits)
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| A1 | Damper calibration has not finished yet. Zoned (multi-zone ducted) systems only. | Normal after a power interruption or new install — the controller calibrates the zone dampers when the system is powered off with the on/off button. It clears itself once calibration completes. | Try this first Switch the system off at the wall controller with the power button and leave it off for a few minutes so the dampers can calibrate. Temperzone's own guidance: if A1 is still there after a week, book a technician. |
| A2 | Damper calibration failed. Zoned systems only. | A fault in the zone damper wiring, a failed damper motor, or incorrect zone setup settings in the controller. | Book a service |
| A3 | The zone controller and the outdoor unit controller are not talking to each other. Zoned systems only. | Zone controller not correctly connected to the outdoor unit controller, or the communication settings of the zone controller do not match the outdoor unit. | Book a service |
| t1 | The temperature sensor built into the SAT-3 wall controller has failed. | The controller is set to use its internal room sensor but that sensor is faulty. The system will read room temperature incorrectly or not at all. | Book a service |
| t2 | SAT-3 external temperature sensor fault — the controller is configured to use an external sensor and that sensor has failed. | Failed or disconnected external sensor, or the controller configured for one that isn't fitted. (t1 is the equivalent fault on the SAT-3's internal sensor.) | Book a service |
| t3 | The SAT-3 wall controller has lost communication with the system. | Wiring between the SAT-3 and the unit controller (non-zoned) or zone controller (zoned) is faulty, or the communication settings do not match. Often accompanies fault F21 on the outdoor board. | Try this first Turn the system off at the switchboard breaker, wait a full 2 minutes, then switch back on. If t3 returns, it is a wiring or settings fault — book a technician. |
Protection trips shown as words on the UC8/UC7 outdoor controller
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| CRH (also shown as F40) | High compression ratio protection — the compressor is working across too big a pressure gap. | Airflow over the indoor and/or outdoor coil is obstructed; indoor or outdoor fan speed too low; incorrect refrigerant charge; expansion valve not opening far enough; faulty pressure transducers or temperature sensors. | Try this first Clear obstructions: clean the return-air filter, make sure supply and return grilles are not blocked by furniture or curtains, and clear plants, fences and debris from around the outdoor unit. If it returns, book a technician. |
| CRL (also shown as F41) | Low compression ratio protection — the pressure difference across the compressor is too small. | The unit is being run at too low a duty; the expansion valve is open too far; faulty pressure transducers or temperature sensors; incorrect DIP switch settings. On some models it also indicates the compressor is not starting. | Book a service |
| FROSt (alt. F3) | Indoor coil frost protection is active — the indoor coil is getting cold enough to ice up, so the unit is protecting itself. | Blocked air filter is the number one cause. Also closed zone dampers, indoor fan speed set too low, or lack of refrigerant. | Try this first Clean or replace the return-air filter and open up more zones so there is enough airflow across the coil, then run the system on fan-only for 20-30 minutes to melt any ice. If FROSt returns with a clean filter, book a technician. |
| Flood | Flooded condensate sump / sump pump fault (UC8 fault number 7). The condensate tray float switch has operated and stopped the compressor to prevent an overflow. | Blocked condensate drain pipe, failed condensate lift/sump pump, drain not U-trapped or run above tray level, faulty float switch. | Try this first |
| HI-SL (alt. F6) | High suction line / evaporating temperature protection is active. | Very high room temperature (cooling) or very high outdoor temperature while running in heating; inadequate insulation on the suction line sensor; faulty suction line sensor; wrong or faulty suction pressure transducer; strain on the transducer cable. | Book a service |
| HI-t (alt. F5) | High temperature protection — the compressor discharge line has become too hot. | Lack of refrigerant (gas leak) is the primary cause; also a faulty or dislodged discharge line temperature sensor (the red-lead sensor), or a malfunctioning/disconnected expansion valve. | Switch off & call |
| HP (alt. F0) | High pressure protection has tripped — refrigerant pressure on the hot side got too high and the unit shut itself down to protect the compressor. | Most commonly the outdoor coil is blocked or the outdoor fan is not running (in cooling), or the return-air filter is blocked / the indoor fan is not running (in heating). Can also be a closed expansion valve, a faulty HP switch or transducer, a closed service valve, or too much refrigerant charge. | Try this first Clean or replace the return-air filter, and clear leaves, grass clippings and any stored items from around and above the outdoor unit so air can move freely. Then power cycle at the breaker for 2 minutes. If HP comes back, stop resetting and book a technician. |
| Hi-dSH (alt. F33) | High discharge superheat protection is active. | Lack of refrigerant (leak); faulty high pressure transducer; incorrect expansion valve DIP switch settings; expansion valve malfunctioning or disconnected. | Book a service |
| LP (alt. F1) | Low pressure protection has tripped — refrigerant pressure on the suction side dropped too low. | The first and most likely cause is a lack of refrigerant, i.e. a gas leak. Other causes: expansion valve closed or its coil not fitted properly, damaged valve wiring, faulty LP switch or transducer, closed service valve, indoor fan not running or too slow (cooling), blocked filter (cooling), outdoor fan not running or outdoor coil blocked (heating). | Book a service |
| Lo-dSH (alt. F9) | Low discharge superheat protection — liquid refrigerant risks returning to the compressor. | Unit overcharged with refrigerant; discharge line temperature sensor not fitted correctly or faulty; incorrect DIP switch settings for the expansion valve; expansion valve malfunctioning. | Book a service |
| Lo-t | Water freeze protection is active (UC8 fault number 4). Applies to hot water heat pumps, hydronic and chiller models. | Insufficient water flow through the heat exchanger, or water temperature sensors dislocated from the pipe. | Book a service |
| Lockout | The unit has locked itself out after a serious fault repeatedly stopped it. The compressor and fans will not run at all. | A protection trip (typically HP, LP, OL, HI-t or a superheat fault) that keeps recurring. The underlying fault has not been fixed. | Try this first Switch off at the switchboard breaker, wait 2 minutes, switch back on. Note: if the unit has locked out three times in a row without completing a cooling or heating cycle, a power cycle will NOT clear it — it then needs the pushbutton on the controller board pressed, which is a service call. Repeated lockouts always mean book a technician. |
| OL (alt. F2) | Overload protection is active — a motor overload or safety switch has opened (input IN#2 is open circuit). | Indoor fan overloaded, outdoor fan overloaded, or the compressor has overheated. Also caused by wiring faults at the overload input. Compressor overheating can be due to incorrect refrigerant charge or poor oil return. | Switch off & call |
| diFF-P | Not a fault — a hold message. The pressure differential across the system is too high to let the inverter compressor start, so it's waiting for pressures to equalise. | Normal after a recent shutdown. The fault relay is not triggered and the system starts on its own once pressures settle. | Try this first Wait a few minutes — it clears itself. No action needed unless it never starts. |
| nO-Flo (No-Flo) | No circulating water flow — circulating pump fault or water flow verification switch fault (UC8 fault number 8). Hot water heat pumps and chillers only. | Circulating pump not running or failed, isolation valve closed, air lock or blockage in the water circuit, faulty flow switch. | Book a service |
Sensor and pressure transducer faults (F12–F20)
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| F12 | Low pressure transducer fault. The controller cannot trust the suction-side pressure reading. It will often display as LP as well. | Transducer cable disconnected or damaged, faulty transducer, or a complete loss of refrigerant. Treat the same way as an LP fault. | Book a service |
| F13 | High pressure transducer fault. The controller cannot trust the discharge-side pressure reading. It will often display as HP as well. | Transducer cable disconnected or damaged, faulty transducer, or a complete loss of refrigerant. Treat the same way as an HP fault. | Book a service |
| F14 | Compressor suction line temperature sensor (SL) fault. | Loose connection at the controller board, or a failed sensor. | Book a service |
| F15 | Compressor discharge line temperature sensor (DL) fault. | Loose connection at the controller board, or a failed sensor (the red-lead sensor). | Book a service |
| F16 | De-Ice temperature sensor fault (DEI input). | Failed or disconnected de-ice sensor. Distinct from F17, which is the outdoor coil temperature sensor on a separate controller terminal. | Book a service |
| F17 | Outdoor coil temperature sensor (OC) fault. On hydronic MWC/MWH/MWR models this code instead means leaving water temperature sensor fault. | Loose connection or a failed sensor. | Book a service |
| F18 | Indoor coil temperature sensor fault (IC input) on air-to-air systems. | Failed or disconnected indoor coil sensor. On MWC/MWH/MWR hydronic models only, this terminal is used for water temperature sensing instead. | Book a service |
| F19 | Outdoor ambient temperature sensor (AMB) fault. | Loose connection or a failed sensor. | Book a service |
| F20 | Superheat is unknown — the controller does not have enough valid sensor data to calculate superheat and manage the expansion valve safely. | A missing or faulty sensor, or wrong DIP switch settings. The technician must check DIP switches, the low and high pressure transducers, the suction line, discharge line, outdoor coil and indoor coil sensors, and all sensor connections. | Book a service |
Communication and configuration faults (F21–F27, F36–F38, F44, F46)
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| F21 | The wall thermostat has stopped communicating with the outdoor controller. | Loose or damaged control wiring between the wall controller and the unit, or electrical interference. On a TZT-100 the satellite-dish symbol will have disappeared from the display; on a SAT-3 you will usually see t3 at the same time. | Try this first Switch the system off at the switchboard breaker, wait 2 minutes and switch back on. If the fault returns it is a wiring or settings problem — book a technician. |
| F22 | Communications lost with the building management system or with system 1 (the master unit). | Loose wiring, the master unit or BMS controller is switched off, or the BMS is communicating too infrequently (it must communicate at least once every 5 minutes). Mainly a light-commercial, multi-unit configuration. | Book a service |
| F23 | Communications lost with system 2 (the first slave unit) in a multi-compressor installation. | Loose wiring between controllers, or incorrect DIP switch settings on the slave board. | Book a service |
| F24 | Communications lost with system 3 (the second slave unit) in a multi-compressor installation. | Loose wiring between controllers, or incorrect DIP switch settings on the slave board. | Book a service |
| F25 | Communications lost with system 4 (the third slave unit) in a multi-compressor installation. | Loose wiring between controllers, or incorrect DIP switch settings on the slave board. | Book a service |
| F26 | Invalid DIP switch setting on the controller. | Controller DIP switches set to a combination the software doesn't accept — usually a commissioning error after a board swap. Older documentation words this as a problem reading the DIP switches. | Book a service |
| F27 | Invalid fan selection — the DIP switches are set to a combination of indoor and outdoor fan types the controller does not support. | Incorrect DIP switch settings, usually a commissioning or board-replacement error. | Book a service |
| F28 | An operating mode has been requested that the unit cannot do. On UC8 this typically means heating was requested from a cooling-only unit, or the unit lacks the outdoor coil de-ice sensor needed for heating. On UC7 the same code means invalid economiser selection. | Thermostat or controller configured for reverse cycle on a cooling-only unit, missing de-ice sensor, or an incorrect controller setting. | Book a service |
| F36 | Invalid DIP switch setting inside the TZT-100 wall thermostat. | The TZT-100 must be set to 1-stage operation (even on multi-compressor units), heat-pump equipment type, and reverse cycle valve ON for heating. If DIP switch 4 (reverse cycle valve ON when heating) is OFF, the controller reports F36. | Book a service |
| F37 | Communication with the indoor unit controller (IUC) has been lost — the outdoor and ducted indoor units are not talking. | No power at the indoor unit, faulty wiring between indoor and outdoor units, or high electrical interference on the control cable. | Try this first Check the indoor (ceiling/roof-space) unit's isolator or breaker is on — it is a separate supply from the outdoor unit and is a common trip point. Then power cycle both for 2 minutes. If F37 returns, book a technician. |
| F38 | The indoor unit controller (IUC) is reporting a fault of its own. | A fault detected inside the ducted indoor unit. The specific problem is indicated by the flash pattern on light L1 on the indoor unit's board (see series notes for the flash-counting table) — typically a T1–T6 sensor fault, an overheating board, or a supply voltage problem. | Book a service |
| F44 | Invalid electronic expansion valve (EEV) mode selection. | Controller configured with an EEV mode the unit doesn't support — a commissioning or configuration error rather than a component failure. | Book a service |
| F45 | Reserved in current UC8 firmware (4.0.6E). In earlier water-cooled model documentation it was listed as 'Low evaporating temperature — not in use'. | Should not appear in service. If seen, it indicates a firmware or configuration anomaly. | Book a service |
| F46 | No communications with the 6-temperature sensor board (6TB). Later software / specific models only. | Wires disconnected between the controller and the temperature board. | Book a service |
Fan, controller board and electrical supply faults
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| F10 | Outdoor fan fault — the outdoor fan is not running as commanded. | Fan motor, capacitor, wiring or fan controller fault; can also be caused by something physically jamming or obstructing the fan. | Try this first With the system switched OFF at the breaker, look for leaves, plastic bags, garden debris or rubbish blocking or fouling the outdoor fan and coil, and clear it. Do not put hands inside the unit. If the fan still does not run once power is restored, book a technician. |
| F11 | Indoor fan fault — the ducted indoor fan is not running as commanded. | Fan motor, EC fan controller, wiring or fan speed configuration fault. | Book a service |
| F29 | The controller board's microprocessor is too hot (over about 100°C). | Extremely high temperature inside the electrical compartment — poor ventilation of the electrical box, or another heat-generating fault. The documented remedy is to find the cause and wait for the unit to cool down. | Book a service |
| F30 | Supply voltage to the controller is out of bounds — the board is not getting a stable, correct voltage. | Mains supply voltage too low (the board needs a stable 230V AC), or excessive current being drawn from the controller's 12V DC supply, e.g. a short circuit in the thermostat wiring. | Switch off & call |
| F31 | A slave unit in a multi-compressor system is reporting a fault. | The real fault is on the slave unit's own controller — that board must be read to find the actual code. | Book a service |
| F32 | Controller internal fault. On UC7 (and in the UC8 Issue-4 operation manual) this code means a 0-10V input fault instead — check the label on the board. | As an internal fault: moisture or dirt on the circuit board, or a failed board. As a 0-10V input fault: lost communications to the 0-10V input module, or the module is not plugged in properly. | Book a service |
Refrigeration system faults
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| F34 | Problem with the pressure transducer readings, or the high and low pressures are not equalising when the compressor is off. | Transducer wires swapped, transducers fitted to the wrong pipe, incorrect transducer type fitted, expansion valve stuck closed, or a faulty transducer. Often first flagged during a test-mode pressure comparison. | Book a service |
| F35 | Reverse cycle (4-way) valve fault — the valve that switches the system between cooling and heating is not doing what it is told. | The unit is running in the wrong mode (cooling when heating was asked for, or vice versa) due to wiring to the reverse cycle valve, or a failed reverse cycle valve. On multi-compressor units it can also be coil sensor readings being influenced by the other refrigeration circuit. | Book a service |
| F42 | Evaporating temperature too high. Related to the HI-SL protection. | Very high room temperature in cooling or very high outdoor temperature in heating; a malfunctioning or disconnected expansion valve; sensor or transducer problems. | Book a service |
| F43 | Condensing temperature too low. | High indoor fan speed with very cold air entering the indoor coil in heating; strong cold wind blowing onto the outdoor coil in cooling; expansion valve open too far; faulty pressure transducers or temperature sensors. | Book a service |
Variable-speed (inverter) compressor driver faults — F39 and the F100 series
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| F39 | The variable-speed compressor driver (inverter) is reporting a fault, or the controller has lost communication with it. | Inverter overheated (blocked heatsink airflow), inverter overloaded, compressor failed to start, an attempt to start against a high pressure differential, or inverter wiring problems. | Switch off & call |
| F100 | No communications between the inverter drive and the unit controller. | No power to the drive, communications cable disconnected, or incorrect DIP switch settings inside the drive. | Book a service |
| F101 | Compressor motor over-current — the compressor is drawing more current than allowed. | Incorrect compressor model selected in the controller, insufficient airflow over the coils, or a fan malfunction. | Switch off & call |
| F102 | Compressor motor overload. | The compressor is being worked beyond its safe limit, commonly from restricted airflow, incorrect charge or an incorrect compressor model selection. | Switch off & call |
| F103 | Over-voltage at the drive. (On units with an Emerson CSD100 driver, F103 instead means motor current too high.) | Mains supply voltage too high. | Switch off & call |
| F104 | Under-voltage at the drive. | Mains supply voltage too low. | Switch off & call |
| F105 | Drive too hot. (On Emerson CSD100 units, F105 instead means driver internal power supply fault.) | Insufficient cooling of the drive — obstructed heatsink airflow or a blocked electrical compartment. | Book a service |
| F106 | Drive too cold to operate safely. | Ambient temperature at the drive below its operating range. | Book a service |
| F107 | Drive over-current. | Incorrect compressor model selected, insufficient airflow, or a fan malfunction. | Switch off & call |
| F108 | Compressor motor too hot. | Overheating compressor, commonly from restricted airflow, incorrect refrigerant charge or poor oil return. | Switch off & call |
| F109 | Reserved Power+ inverter drive alarm code. Listed by Temperzone but not assigned a function. | Should not appear in normal service. | Book a service |
| F110 | Drive internal error. | Internal failure within the inverter drive. | Book a service |
| F111 | Incorrect parameter programmed in the drive. | Incorrect compressor model selected in the controller's compressor-model setting. | Book a service |
| F112 | Excessive DC bus ripple in the drive. | Unbalanced mains phase voltages on the incoming supply. | Switch off & call |
| F113 | Communication fault with the drive. | Communications cable disconnected or damaged. | Book a service |
| F114 | Internal fault in the drive. | Internal failure within the inverter drive. | Book a service |
| F115 | Auto-tuning fault — the drive could not successfully tune itself to the compressor motor. | Wiring, compressor or configuration problem detected during the drive's tuning routine. | Book a service |
| F116 | The drive is disabled — the safe-torque-off (STO) input is open circuit. | The wire links to the drive's enable input have been disconnected. | Book a service |
| F117 | Motor phase fault — one of the compressor motor phases is missing or faulty. | A loose or disconnected compressor motor wire, or a compressor winding fault. | Switch off & call |
| F118 | Internal cooling fan fault inside the inverter drive. | Faulty fan in the drive, which will lead to the drive overheating if not fixed. | Book a service |
| F119 | Speed fault — the compressor is not running at the speed the drive commanded. | Drive, compressor or feedback fault. | Book a service |
| F120 | Power factor correction circuit overload in the drive. (On Emerson CSD100 units, F120 instead means motor too hot.) | Overload of the drive's input circuitry, often supply-related. | Switch off & call |
| F121 | Mains input voltage too high. | Incoming supply voltage above the drive's limit. | Switch off & call |
| F122 | Mains input voltage too low. | Incoming supply voltage below the drive's limit — brownout, undersized supply or a poor connection. | Switch off & call |
| F123 | Drive internal fault. | Internal failure within the inverter drive. | Book a service |
| F124 | Reserved Power+ inverter drive alarm code. Listed by Temperzone but not assigned a function. | Should not appear in normal service. | Book a service |
| F125 | High earth current fault — the drive is detecting current leaking to earth. | An earth leakage fault in the compressor motor windings or the drive wiring. This is an electrical safety fault. | Switch off & call |
| F126 | Drive processor overload. | Internal fault within the inverter drive. | Book a service |
| F127 | Drive memory loss — the drive has lost its stored configuration. | Internal fault in the drive; it will need reconfiguring. | Book a service |
| F128 | Drive overload protection has operated. | The drive has been run beyond its rated output, commonly from restricted airflow or an incorrect configuration. | Switch off & call |
| F129 | Safety intervention fault in the drive. | A drive safety function has operated to stop the compressor. | Switch off & call |
| F197 | The drive is reporting an incorrect compressor speed. | Drive feedback or configuration problem. | Book a service |
| F198 | Drive and compressor mismatch. (On Emerson CSD100 units, F198 instead means motor phase loss.) | The wrong compressor model is selected in the controller for the compressor actually fitted. | Book a service |
| F199 | Drive configuration fault. | The drive's configuration is invalid. The documented remedy is to remove mains power and then re-apply it so the controller can reconfigure the drive. | Book a service |
Normal display messages often mistaken for faults
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| Flashing dot (•) | Normal operation. The controller is powered, healthy and ready — this is what you want to see. | No fault. Nothing to do. | Try this first No action needed. If the unit is not running while showing a flashing dot, the thermostat simply is not calling for cooling or heating — check the setpoint and mode at the wall controller. |
| Flashing dash (–) | The unit is switched OFF by an external remote on/off signal, not by a fault. | The remote on/off input is open circuit — commonly a building timer, a separate on/off switch, or a disconnected link. | Try this first Check any separate on/off switch, timer or isolator that controls the system, and make sure the wall controller is switched on. If nothing obvious, book a technician. |
| HOLd | The compressor is being deliberately held on or held off by a built-in safety timer. Numbers after HOLd count down the remaining seconds. | Completely normal anti-short-cycle protection after a mode change, a power interruption or a recent stop. It prevents the compressor from restarting too soon. | Try this first Just wait — up to about 6 minutes, and up to 20 minutes after a cooling/heating changeover. Do not keep switching the system off and on, as that restarts the timer. |
| dELAY | The unit is waiting out a short random start-up delay after power was applied. Up to about 20–30 seconds. | Normal behaviour after a power-on. Random delays stop multiple units all starting at the same instant. | Try this first Wait 30 seconds — it clears itself. |
| dE-ICE | The outdoor coil is being de-iced. Normal winter behaviour in heating mode. | The de-ice sensor read below about -4°C while heating, so the unit briefly reverses to melt ice off the outdoor coil. Steam from the outdoor unit and a pause in warm air are normal during this. | Try this first Wait — a de-ice cycle ends when the coil reaches +12°C or after a maximum of 10 minutes. If the unit de-ices constantly, make sure the outdoor unit is clear and sheltered from strong cold wind, then book a technician if it continues. |
| dr | A DRED energy restriction is active — the electricity supplier's demand-response signal is limiting the unit. | Normal operation of a demand response enabling device. Depending on the signal the compressor may be switched off, or energy use reduced by about 25% or 50%. | Try this first Wait for the restriction period to end — this is controlled by the electricity supplier, not the air conditioner. If DRED was never meant to be connected, a technician can check the D1/D2/D3 inputs. |
| ctrL | A slave controller is waiting for the master controller to take control. Multi-compressor systems only. | Normal start-up state in a master/slave installation. If it persists, the master is not communicating. | Try this first Power cycle at the breaker for 2 minutes. If ctrL stays on the display, book a technician. |
| t / c | The controller is in test mode (t, about 1 minute) or commissioning mode (c, up to 30 minutes) — an engineer setting, not a fault. | Someone has held down the controller pushbutton, or a technician left the unit in commissioning mode after a service visit. Safety timers are shortened while c is displayed. | Try this first It times out by itself — test mode after about a minute, commissioning mode after 30 minutes, or immediately if power is cycled at the breaker. |
| UC8 X.X.X (e.g. UC8 4.0.6) | Controller name and software version, shown briefly every time the outdoor unit is powered on. | Normal power-on display. Follows a power cut or the isolator being switched on. | Try this first |
| SLP | Information readout: compressor suction line pressure in kPa. | Someone has pressed the push button on the outdoor controller to cycle through the monitoring readouts. | Try this first |
| Et | Information readout: evaporating temperature in degrees C. | Push button pressed to cycle through monitoring readouts. | Try this first |
| SLt | Information readout: compressor suction line temperature in degrees C. | Push button pressed to cycle through monitoring readouts. | Try this first |
| SSH | Information readout: suction (evaporating) side superheat in K. | Push button pressed to cycle through monitoring readouts. | Try this first |
| dLP | Information readout: compressor discharge line pressure in kPa. | Push button pressed to cycle through monitoring readouts. | Try this first |
| Ct | Information readout: condensing temperature in degrees C. | Push button pressed to cycle through monitoring readouts. | Try this first |
| dLt | Information readout: compressor discharge line temperature in degrees C. | Push button pressed to cycle through monitoring readouts. | Try this first |
| dSH | Information readout: discharge (condensing) side superheat in K. | Push button pressed to cycle through monitoring readouts. | Try this first |
| ICEt | Information readout: outdoor coil de-ice sensor temperature in degrees C. | Push button pressed to cycle through monitoring readouts. | Try this first |
| CAP | Information readout: compressor capacity as a percentage. | Push button pressed to cycle through monitoring readouts. | Try this first |
| EE1 / EE2 | Information readout: electronic expansion valve 1 / valve 2 opening as a percentage. | Push button pressed to cycle through monitoring readouts. | Try this first |
| Add | Information readout: the controller's Modbus communications address. | Push button pressed to cycle through monitoring readouts. | Try this first |
| H | Configuration mode: indoor fan high speed selection. Entered by holding the push button on the outdoor controller. | Push button held down, usually accidentally, while the thermostat and compressor are off. | Try this first |
| L | Configuration mode: indoor fan low speed selection. | Push button held down while the thermostat and compressor are off. | Try this first |
| A | Configuration mode: Modbus communications address selection. | Push button held down while the thermostat and compressor are off. | Try this first |
| E | Configuration mode: compressor model selection. Leads on to codes such as dF, 010, 3-550 or 1-240. | Push button held down while the thermostat and compressor are off. Changing this setting can damage the compressor. | Book a service |
| d | Configuration mode: force an outdoor coil de-ice cycle (only available while the unit is heating). Distinct from the dE-ICE running message. | Push button held down during heating operation. | Try this first |
| J | Configuration mode: outdoor fan chamber selection on air-to-air units (water flow valve opening time on hydronic units). | Push button held down while the thermostat and compressor are off. | Try this first |
| Y | Configuration mode: supply-air temperature control mode selection. | Push button held down while the thermostat and compressor are off. | Try this first |
| b | Configuration mode: communications baud rate selection. | Push button held down while the thermostat and compressor are off. | Try this first |
| P | Configuration mode: communications parity and stop-bit selection. | Push button held down while the thermostat and compressor are off. | Try this first |
| o | Configuration mode: thermostat automatic on/off selection (SAT-3 and TZT-100 only). | Push button held down while the thermostat and compressor are off. | Try this first |
| n | Configuration mode: expansion valve mode selection (split air-to-air units only). | Push button held down while the thermostat and compressor are off. | Try this first |
| bC0 / bC1 / bH0 / bH1 | Configuration modes for batch water heater switch-off and switch-on temperatures in cooling and heating. Hot water heat pump models only. | Push button held down while the thermostat and compressor are off. | Try this first |
| dF, 010, 3-38S, 3-38L, 3-550, 3-066, 3-078, 3-087, 3-656, 3-096, 1-030, 1-038, 1-132, 1-240 | Compressor model identifiers shown inside the 'E' compressor model selection mode — not fault codes. For example dF = digital scroll or fixed capacity, 010 = 0-10V inverter compressor, 1-240 = Panasonic 5KD240. | The controller has been left in E mode. Selecting the wrong model here will cause CRL/F198 faults or compressor damage. | Book a service |
SAT-3 wall controller trouble codes
| Code | What it means | Likely cause | What to do |
|---|---|---|---|
| A1 A2 | Invalid thermostat configuration / TZT-100 DIP switch setting (UC8 F36). | Thermostat DIP switches not set to 1-stage, heat-pump equipment type, reverse cycle valve ON for heating. | Book a service |
| A1 A2 / A1 A3 / A2 A3 / A1 A2 A3 | Combinations of the zone-controller faults A1, A2 and A3 occurring together. Digits are always read lowest to highest, and each is shown twice before repeating. | Two or more of: damper calibration not completed, damper calibration failed, comms lost between zone controller and outdoor unit. | Book a service |
| A1 A2 A4 | Communications lost with the thermostat (UC8 F21). Temperzone notes this code usually cannot actually be shown, because the SAT-3 is the device that has lost comms. | Damaged or loose RS485 wiring between the wall controller and the unit. | Book a service |
| A1 A2 A5 | All other UC8 faults (internal fault numbers 44–47). Temperzone notes this 'should never be seen'. | Undefined/reserved controller fault. Read the actual code on the outdoor unit display. | Book a service |
| A1 A2 A6 | A controller configuration or board fault — one SAT-3 code covering UC8 F26, F27, F28, F29, F30 and F32. | Cannot read DIP switches, invalid fan selection, controller board too hot, supply voltage out of bounds, or an internal controller problem. | Book a service |
| A1 A2 A8 | Superheat unknown (UC8 F20) — the controller cannot calculate superheat. | A missing or failed sensor/transducer, or incorrect DIP switch settings. | Book a service |
| A1 A4 | High pressure (HP) trip reported by the outdoor unit — the SAT-3 alternates A1 A1 A4 A4. | Blocked or dirty outdoor coil, outdoor fan not running, indoor fan not running in heating, blocked filter, overcharge, faulty HP transducer/switch. | Try this first |
| A1 A5 | Low pressure (LP) trip reported by the outdoor unit. | Loss of refrigerant (gas leak), closed service valve, blocked return-air filter or dampers closed in cooling, EEV closed/disconnected, faulty LP transducer. | Book a service |
| A1 A6 | Indoor coil frost protection active (UC8 shows FROSt). | Blocked/dirty air filter, too many zones closed, indoor fan speed set too low, or low refrigerant charge. | Try this first |
| A1 A7 | Compressor high discharge line temperature protection (UC8 shows HI-t). | Lack of refrigerant, faulty discharge line sensor, EEV malfunction. | Book a service |
| A1 A8 | High suction line temperature protection (UC8 shows HI-SL). | Very high room temperature in cooling, heating attempted at high outdoor ambient, damaged sensor insulation, faulty suction line sensor. | Book a service |
| A2 A3 | Reverse cycle valve fault (UC8 F35) — the unit may be running in the opposite mode to the one selected. | Failed or stuck reversing valve, disconnected valve coil, or an incorrectly fitted coil temperature sensor. | Book a service |
| A2 A3 A4 | A slave unit reports a fault (UC8 F31) — on multi-compressor systems. | One of the slave systems has its own active fault; read the fault code on that unit's own controller. | Book a service |
| A2 A4 | Communications lost with the BMS / master controller (UC8 F22). | Loose RS485 wiring, master unit or BMS switched off, intermittent communications. | Book a service |
| A2 A5 | Communications lost with system 2 (first slave unit) — UC8 F23. | Loose inter-unit RS485 wiring or incorrect DIP switch system numbering. | Book a service |
| A2 A6 | Communications lost with system 3 (second slave unit) — UC8 F24. | Loose inter-unit RS485 wiring or incorrect DIP switch system numbering. | Book a service |
| A2 A7 | Communications lost with system 4 (third slave unit) — UC8 F25. | Loose inter-unit RS485 wiring or incorrect DIP switch system numbering. | Book a service |
| A2 A8 | Communications lost with the indoor unit controller (IUC) — UC8 F37. | RS485 wiring between indoor and outdoor unit disconnected, or no power to the indoor unit board. | Book a service |
| A3 A4 | Low discharge superheat protection (UC8 shows Lo-dSH). | Overcharged system, discharge sensor not fitted correctly, incorrect EEV DIP switch settings. | Book a service |
| A3 A5 | High discharge superheat protection (UC8 shows Hi-dSH / F33). | Lack of refrigerant, faulty HP transducer, incorrect EEV DIP switch settings. | Book a service |
| A3 A6 | Overload (OL) protection trip. | Indoor or outdoor fan overloaded, obstructed airflow, compressor overheated, or the IN#2 overload input has gone open circuit. | Try this first |
| A3 A7 | Outdoor fan fault or indoor fan fault (UC8 F10 or F11). | Seized or failed fan motor, EC fan reporting an alarm, loose fan wiring, obstructed fan. | Book a service |
| A3 A8 | A sensor or pressure transducer fault — covers UC8 F12 to F19 as one SAT-3 code. | Disconnected or damaged sensor/transducer lead, faulty sensor, or complete loss of refrigerant (for the pressure transducers). | Book a service |
| A4 (shown on its own) | Unit is locked out. The outdoor controller has tripped the same protection 3 times and has stopped the compressor and fans until it is manually reset. | Repeated HP/LP/OL/frost trips from an underlying fault — blocked filter or return air, dirty/blocked outdoor coil, low refrigerant charge, failed fan. | Book a service |
| A4 A5 | Compression ratio too high (UC8 CRH / F40). | Pressure transducer fault, EEV malfunction or disconnected, indoor fan or controller malfunction, overcharged system. | Book a service |
| A4 A6 | Compression ratio too low (UC8 CRL / F41). | The compressor is not actually starting, or an incorrect compressor model is selected in the controller. | Book a service |
| A4 A7 | Evaporating temperature / pressure too high (UC8 F42). | EEV malfunctioning or disconnected. | Book a service |
| A4 A8 | Pressures not equalising (UC8 F34) or condensing temperature too low (UC8 F43). | Pressure transducer leads swapped or fitted to the wrong pipe, incorrect transducer type, EEV malfunctioning. | Book a service |
| A5 A6 | Water freeze protection active (UC8 Lo-t). Hot water heat pumps and chillers only. | Insufficient water flow, or water temperature sensors dislocated. | Book a service |
| A5 A7 | Flooded condensate sump (UC8 Flood). Hot water heat pumps only. | Blocked condensate drain, failed sump/lift pump, drain not U-trapped or piped above tray level, faulty float switch. | Try this first |
| A5 A8 | No circulating water flow (UC8 nO-Flo). Hot water heat pumps and chillers only. | Circulating pump not running, closed valve, air-locked or blocked water circuit, faulty flow switch. | Book a service |
| A6 A7 | The variable-speed (inverter) compressor drive is reporting a fault — UC8 F39, with the detail shown as an F100-series code on the outdoor controller. | Any Power+ drive alarm — over/under voltage, over-current, drive too hot, comms loss to the drive. | Book a service |
| A7 A8 | The indoor unit controller (IUC) is reporting a fault — UC8 F38. | An indoor-side sensor (T1–T6) fault, indoor board too hot, indoor supply voltage problem. Diagnose from the IUC L1 LED flash pattern on the indoor board. | Book a service |
No matching code found.
Meanings vary by series and some codes are model-specific — call 0434 951 341 with the code and your model number and we'll decode it.
Reference compiled from Temperzone service and operation documentation. Codes and meanings are provided as general guidance for the Australian residential range and can differ between model series; no affiliation with Temperzone is implied.
Found your code?
Tell us the code when you book — diagnosis starts before we arrive
Fault finding across Perth from $165 inc GST — all brands, splits and ducted. Quoting the fault code gives us a head start on where to look; we then test and confirm the actual fault on site before any part is ordered, so you shouldn't end up paying for a part you didn't need.
The honest next question
Repair or replace your Temperzone?
A fault code tells you something's wrong — it doesn't tell you whether the unit is worth fixing. The age of the system is the honest starting point:
Under ~8 years
Repair usually winsMost fault codes on a young unit trace to something sensible — a sensor, a board, a blocked drain — and a proper diagnosis first means you pay for the diagnosed fault, not guesswork. A Temperzone under eight years old is normally worth fixing.
8–15 years
Get both numbersThis is judgement-call territory. A cheap fix on a working system is still good money — but if the fault is compressor- or inverter-side, the repair can be a third of a new unit's installed price. Ask for the repair quote and the replacement quote together and decide once, with real numbers.
15+ years
Replacement is usually better moneyEfficiency has moved a long way in a decade — a modern unit cools the same room for a fraction of the running cost — and parts supply for older series thins out with age. At this age, money spent on another repair is usually money towards a unit that's near the end either way.
What replacement actually costs: a like-for-like split swap in Perth typically runs $1,700–$3,800 supply and installed — about the same as a first-time install, because decommissioning the old unit (legal refrigerant reclaim, removal, disposal) offsets the saving from reusing the circuit. The existing circuit can usually be reused if it's compliant; pipework is replaced in almost every case, or properly flushed where new runs aren't practical. Full numbers by size are in our Perth cost guide and the installed price directory.
Frequently Asked Questions
What does A1 A4 mean on my SAT-3?
It's a high-pressure trip reported up from the outdoor unit — the same fault the UC8 controller shows as HP. The SAT-3 codes are a summary layer; the table below maps each one to the underlying UC8 fault so you know what a technician will be looking at.
My controller shows A4 on its own — is that different?
Yes, and it matters. A4 alone means the unit is locked out: the outdoor controller has tripped a safety and won't restart until the cause is dealt with. That's a service call rather than something to reset repeatedly.
What does diFF-P mean? It's not in the fault list.
Because it isn't a fault. It's a hold message meaning the pressure differential is still too high for the inverter compressor to start, so the system is waiting for pressures to equalise. It clears itself in a few minutes and the fault relay never triggers.
Does my controller change what the codes mean?
It can. F12 is the low-pressure transducer on a UC8 but the high-pressure transducer on the older UC7, for example. Identify which controller your system has before looking up an F-number — or quote both the code and your model to us and we'll sort it out.
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