To expand a little, the "working" unit is a 2000, the first spare is the 1000 that came with the boat but is a bit pushed in heavy weather, and the spare spare is a 2000 that I bought when the working 2000 failed. I fixed it, however (see earlier posts) and apart from a few minutes trial to prove it worked, the second 2000 has stayed in its box. Even buying all of them new, total cost would be c. £1k as opposed to £2k for a windvane. Not that I haven't thought about trying to build one of the latter: in quiet conditions the only sound can be the noise of the autohelm which would be nice to lose - but not worth £2k!