Same problem for me - I bought a Vantage Vue via Amazon in May 2013. I have the console in myupstairs (home) office by the window so it faces the weather station. The station is on a 12 foot mast, mounted with Y braces to our shed. Had the console go a few years back, so that got replaced. The weather vane got shortened - not sure if it was a bird or what, replaced that. Now the wind speed shows zero mph - for a few months. I got it down and cleaned everything. No change. I ordered the wind speed cartridge - which is basically the shaft (with a magnet on one end?) in a housing. Just had a chance to pull the unit down, pulled the cups off, opened unit, swapped in the new one and - no change!
Tried it twice - no change (tested it by Spinning cups by hand while its still accessible inside my office). Wind vane direction works fine this way.
Anyway, the sensor assembly under the black tower should contain the reed switch - easily accessible. I tried to shim it so its higher in the tower, and closer to the spinning magnet, but not sure what else to do at this point.
I'd hate to have to buy another weather station because a goofy switch failed!