Mitsubishi Ecodan Error Codes
The most common Mitsubishi Ecodan fault codes we encounter: E1 (outdoor-indoor communication error) — often a loose cable connection. E6 (inverter compressor overcurrent) — can indicate a failing compressor or refrigerant issue. E8 (inverter compressor overload) — often caused by restricted airflow or high ambient temperatures.
P1 and P8 codes relate to pressure sensor faults. These can sometimes be resolved by a system reset, but if they recur, the pressure sensor or refrigerant charge needs checking by an F-Gas certified engineer.
Daikin Altherma Error Codes
Daikin systems display errors as alphanumeric codes. Common ones include: U0 (refrigerant shortage or metering device fault), 7H (outdoor fan motor fault), E7 (outdoor fan motor locked), and AH (air purge error). The AH error is frequently seen on new installations where the refrigerant lines weren't properly evacuated.
Daikin errors beginning with 'L' typically relate to the hydraulic module and can often indicate water flow issues rather than refrigerant problems. Check that valves are open and the circulation pump is running before calling an engineer.
Vaillant aroTHERM Error Codes
Vaillant displays fault codes with an 'F' prefix. F.20 to F.28 relate to temperature sensor faults. F.61 and F.62 indicate gas valve faults (relevant for hybrid systems). F.75 relates to water pressure sensor issues — often resolved by repressurising the system.
The Vaillant aroTHERM can be particularly sensitive to water flow rates. Error codes related to high-pressure faults often trace back to partially closed valves, air locks, or an undersized buffer tank rather than a refrigerant issue.
When to Reset vs When to Call
As a general rule: if a fault code appears once and clears after a reset, monitor the system for recurrence. If the same code appears twice within a week, call an engineer. If a code relates to compressor overcurrent, high pressure, or refrigerant shortage, do not reset — call immediately.
Never repeatedly reset a heat pump that keeps faulting. Each fault event can cause additional stress on components, particularly the compressor. Three resets and the same fault should be your maximum before seeking professional help.