Vaisala AWS330 - Manual (Page 191)

Chapter 6 ______________________________________________________________ Maintenance
VAISALA ______________________________________________________________________ 189
0204-045
Figure 112 WAV151 Assembly
The wind vane has been counter-balanced at the factory, but it can be
readjusted if necessary. To do this, loosen the vane assembly and place it
on its side on the table. A correctly balanced vane will stay in horizontal
position.