Ya'll can all just call me "Speedy".
I just now have installed the wind speed cartridge (shaft and bearings assembly)...the prospect of Hurricane Irma arriving in two days encouraged me to "get'er done!". The new cartridge appears to be working well. Though folks south of me are getting plenty of wind it is rather becalmed around here right now so I haven't seen it clock any high speeds yet. Tomorrow, and especially Monday, Hurricane Irma should give it a good test.
As long as you have the allen wrench that came with the station or a set with some *small* ones in it and a medium size phillips screwdriver you have all the tools you need to work on it. Naturally you will need other than the tools to lower the mast with. Simple repair....even "Speedy" did it.
Observations: I found that when I spin the stem of the old cartridge, with nothing attached to it and holding it in my hand, that the shaft/magnet(?) assembly will spin freely but suddenly "hit" something hard causing it to stop spinning. Sometimes when it "hits" it will bounce back spinning a turn or two in the opposite direction. It always "hits" when I spin it in the proper direction. Oddly, when I spin it in the "wrong" direction, opposite of the design of the cups, it spins freely and doesn't "hit". Also, if I hold on to the shaft and turn it while keeping my fingers on it (not simply free-spinning it) I can feel a rough scrubbing and it will lock up at times in either direction.
I think something is inside that has "come lose", be it a ball bearing, a chip of metal, or ????, and it spins until that something jams the shaft or one of the bearings. My old cartridge is not rusty or corroded and other than a small amount of spider web there wasn't any dirt or debris in it...it actually looks good. It just suddenly stops when it when it "hits" that something.
The new one seems to be working good, so hopefully it will be good to go for several more years. The first cartridge lasted just a tad over four years.
I just thought I'd share what I did/found.
Best wishes to all, and to everybody in the path of Irma be safe.
Ed
ETA: Link to the part needed...
https://www.scaledinstruments.com/product/davis-6410-anemometer-for-vantage-pro2-vantage-pro/