BoatBanter.com - View Single Post - Navman 3100 wind indicator erratic at 10knts

Larry

wrote in news:b15daec4-b3e3-44a4-9ae8-72661ab33cc0
@d42g2000prb.googlegroups.com:

This problem was solved by doing a full software reset and
recalibration. It works fine now.

If the problem recurs, listen carefully to your 12V boat stereo while the
alternator is running and when the charger is running. Listen for a
whining noise from the alternator that varies pitch with engine speed. The
alternator will be a low level constant 120 Hz bass note and is harder to
hear.

These noises indicate corroded 12V connections or dead cells in the
batteries, causing series resistance to the charging. It causes any
charging or loading to have an AC component riding on top of the battery DC
voltage. If it gets bad enough, this pulsing (from heavy loads coming on
and off) and whine from the charging, will cause computers hooked to the DC
like your wind computer to scramble its data.

Lightning pulsing the wiring to the wind head from last summer's storms
also causes the computer to become scrambled, without destroying
it...sometimes. It's called EMP (Electromagnetic Pulse) and will render
the whole country electronically dead when the nuclear weapons go off.

If you see the DC lights blinking when a fridge or bilge pump comes on,
that's an indication of the series resistance in the DC battery circuits.