Vaillant aroTHERM fault F.735

What it means

Temperature in the environment circuit (heating mode) or building circuit (cooling mode) too high for compressor operation.

Likely causes

1. Temperature in the environment circuit (heating mode) or building circuit (cooling mode) too high for compressor operation
2. Feed-in of external heat into the environment circuit too high due to increased fan speed
3. Temperature in the environment circuit or building circuit too high for compressor operation
4. No heat requirement via the control
5. Timer programme not set correctly
6. Room temperature at or above target temperature

Where to start

1. Check the system temperatures
2. Check the refrigerant filling volume for overfilling
3. Check the EEV (does the EEV move to the limit stop? Use sensor/actuator test)