It's fairly easy to check whether the windspeed tansducer is working or not. Raymarine has a good description: Raymarine Marine Electronics - Welcome
Of course, in your case, you won't need a separate power supply, as the instrument supplies the power, but everything else in the above description works for you.
The speed transducer is in fact producing pulses, so depending on the type of the voltmeter you may be using, you will see voltage variation between 0 and 5 volt (approx), or, especially if it is turning slowly, jumps between high and low voltage. If it is constantly around 0 or 5, then you have a problem. Check connections and cable continuity everywhere (including at the instrument terminals and the masthead!), as faulty connections are far the most common problems of erratic wind indication.
I just finished what is likely my last sail weekend of the season and had a couple oddities occur (better the end of the season than the beginning). For this forum category, I'll stick to the topic.
My ST60 wind display suddenly went to 0.0 when I changed from true to apparent and never came back up. It occurred at the exact moment I pushed the button. The direction indicator is fine and points the correct direction and is calibrated. The masthead unit is turning but 0.0 never changes. I've powered down and back on with no luck. I'd prefer not to re-calibrate it, but I will if I have to.
I've looked for a similar thread, but the ST60 topics are all over the place. I do notice that many people report dashes on the display while mine says 0.0.
Thanks for any help
sv Island Breeze