The supervisor message aSU shows you continuously monitored information about rain and wind sensor heating (heating temperature Th and heating voltage Vh).
The heating temperature should stay above 0 °C when the heating is on (except in extremely cold conditions where the heating power is not sufficient). The heating voltage Vh should correspond to the heating voltage supplied. If there is a remarkable deviation, check the wiring. Note that wire gauge should be large enough to avoid remarkable voltage drop in the cable.
In case AC or full-wave rectified AC is used for the heating, the Vh measurement behaves as follows:
While heating is off, Vh indicates the positive peak value (Vp) of the heating voltage waveform.
While heating is on, Vh indicates: