Mitsubishi Ecodan fault 33

What it means

The unit runs in Cooling mode when outdoor ambient temperature is lower than 10 degrees C, outside the guaranteed operating range. When defrosting operation runs at such low outdoor ambient temperature after Cooling mode switches to DHW or LP mode, the water temperature in the cooling circuit drops too low, resulting in L6 error that stops all operations.

Likely causes

1. Unit runs in Cooling mode when outdoor ambient temperature is lower than 10°C (outside guaranteed operating range)
2. Defrosting operation running at low outdoor ambient temperature after switching from Cooling to DHW or LP mode causes cooling circuit water temperature to drop too low

Where to start

1. Check outdoor ambient temperature relative to 10°C threshold
2. Check freeze stat function preset temperature settings if automatic stop/recovery of cooling operation is desired