I have the later model of anemometer with no reed switch, bought in September 2013 shortly after it came out. However, for a while now the wind cups have been 'sticking' at times in light winds. Looking back through my records, the first sign of this was actually in summer 2014, though gradually getting more noticeable, especially this winter.
For the first year or so after purchase, the 'gust' would very rarely be 0mph. Now however, it can be zero for nearly the whole night except for occasional spike of 4-8mph. I have also noticed a visible light breeze (plants moving etc) with the vane moving but no movement of the cups. Sometimes, by shaking the pole lightly, it frees the cups and off they go briefly, or they 'stutter' and try to turn irregularly before stopping.
Oddly, the sticking issue is not continuous and I sometimes see them spinning/gliding freely at 1-2mph (as opposed to irregular stop/start movements), perhaps after a stronger gusts have 'freed' them, though this lasts a variable period until they stop and stick.
A few days ago this finally prompted me to get the pole down, take the wind cups off and clean the shaft/cups and other exposed surfaces.
However, this does not seem to have solved the problem.
With the wind cups off I took this picture.. and it appears what I think may be the bearings? have some 'rust' or corrosion on them:
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I was wondering if this is likely to be the cause, or could it be something else such as dirt/dust getting further into the 'body' behind what is visible with just the cups off?
The shaft turned freely, with no noticeable stiffness or grittiness, though made a noise if I 'span' it at high speeds.
This anemometer is a replacement for another which did this same thing after 1 year 4 months! Indeed I made a very similar post to this one. I thought maybe it was a one off and bought the new version hoping it would last several years.. so it will be a bit annoying if this is the bearings or it is not easily fixable..
Despite my need for accuracy, if it is the bearings I could probably live with it compared to paying the UK price for a new anemometer.. unless it is likely to affect higher wind speeds too?
Though it would be nice to have a properly functioning part so I'm happy to hear any suggestions from people who get to the end of this longer than intended post (bearing in mind (pun unintended!) I don't really have any DIY experience with these things).
Many thanks
Sam