John Seager wrote:
"John Seager" wrote in message
...

I have an old Autohelm Wind Speed instrument (analogue direction with
digital speed) which no longer works. The direction needle moves, but does
not settle in any clear relation to the wind, and wind speed reads 0. I'd
like to see if there is any signal coming from the masthead unit before
going aloft and stripping the whole wiring out. Does anyone know what
voltages I should expect for the various wires coming down the mast? There
is a convienient junction box, so I don't need to cut into the wires to do
this.
TIA,
John.

I think the model is an ST50, if that helps.
J


If I remember correctly, the speed is a pulse signal and the direction
is two signals with voltages corresponding to the SINE and COSINE of the
angle of the windvane. There is an 8 volt supply fed up the mast from
the display head to power the masthead unit and the direction signals
swing from somewhat above zero to a bit less than the supply. The
symptoms you have indicate a missing supply or ground to the masthead
unit. It may be a failed display head or bad wiring or possibly a
failed masthead unit.

The display head and masthead unit are often repairable (although
raymarine wont be any help - you need a good independent, preferably
working for beer money rather than commercially) and the wiring can be
replaced. If you do end up ripping it out, as the ST50 wind transducer
is discontinued, someone here may well be interested in it for spares.