Display shows E16; heater does not start and may indicate low ambient conditions.

Safety first: No internal work is usually required for this code.

• Check outdoor temperature: Compare the displayed ambient temperature with an external thermometer. If the real temperature is below the specified minimum, the unit is correctly locked out.
• Verify sensor accuracy: If the display shows an unrealistically low temperature, inspect and test the ambient sensor as described for E07.
• Review settings: Ensure that any winter or low‑temperature operating modes are configured according to the Hewalex manual.
• Wait for warmer conditions: If conditions are genuinely too cold, wait until ambient temperature rises into the allowed range before restarting.