MasterTherm · A niche brand in the UK. 16 codes across 2 product families, each taken from the manufacturer’s manuals. MasterTherm technical support ↗
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Type the code on your display or a word from its meaning. Each code opens its own page with what it means, whether it is safe and what you can check.
16 codes
| Code | Meaning | Stops? | Homeowner check? |
|---|---|---|---|
| AL01 | Low Pressure - compressor low suction pressure | Yes | Yes |
| AL02 | High Pressure PT - compressor high discharge pressure from pressure transducer | Yes | Yes |
| AL03 | High Discharge Temperature - high compressor discharge gas temperature | Yes | Yes |
| AL04 | High Condensing Temperature in heating/cooling mode | Yes | Yes |
| AL05 | Low Evaporating Temperature in heating/cooling mode | Yes | Yes |
| AL06 | Antifreeze - low (heating/cooling) water temperature with risk of freezing | Yes | Yes |
| AL07 | Fan Thermal - fan overheating or fan circuit breaker activation | Yes | Yes |
| AL08 | Compressor Thermal - compressor overheating or circuit breaker activation | Yes | Yes |
| AL09 | Flow - insufficient or no flow of water through heat pump | Yes | Yes |
| AL10 | Probes - malfunction of one of the important temperature sensors | Yes | Yes |
| AL11 | High Pressure Switch - compressor high discharge pressure from high pressure switch | Yes | Yes |
| AL12 | Low Pressure HP side - too low pressure on high-pressure side of refrigerant circuit | Yes | Yes |
| AL13 | DC Drive Alarm - alarm of the compressor inverter drive (inverter units only) | Yes | Yes |
| AL14 | EVD Evo - alarm of the Electronic Expansion Valve driver | Yes | Yes |
| AL15 | R290 refrigerant leak - alarm of the refrigerant leak or leak detector malfunction | Yes | Yes |
| E! | E! on main screen - electric (auxiliary) heater safety thermostat activated; heater cannot switch on | Partly | Yes |