erratic wind reading

[samwise]

This week I installed the replacement display unit for my Navman 3100 wind instrument. The display unit is coded as a 3100s which means that is it essentially the Northstar unit and should not suffer from the failing LCD display that afflicted the previous instrument.
However, upon connecting up through the Navbus I am getting some wildly fluctuating readings for both direction and speed.
At times it will settle down and deliver sensible readings that coincide with a handheld wind speed unit and with the Windex direction. Then it goes berserk with direction swinging 40-50 degrees and sometimes round the clock. Speed goes from 16 (what we were actually getting yesterday) to minus 2 or another spurious number.

I have hooked up the old instrument ( which I know worked, apart from the LCD) and get the same wild fluctuations, so I assume the head unit is ok .

It looks like an intermittent short of some kind. Any ideas? It could be a problem with the masthead unit or maybe the deck plug. Grateful for any thoughts and suggestions

 

[Eygthene]

The fluctuations in direction and windspeed would be expected if the boat is rolling in lightish winds and the averaging time of the display is set to a low setting.

You can check if this is the cause. Look up at the mast-top sensors and see if the direction vane is swinging and the cups going round fast and slow when the readings are fluctuating.

If so, you can get steadier readings by increasing the averaging time of the display in the instrument set-up menu.

 

[radarman]

I would also check your deck connections as it could be caused by them being intermittent. I take it you haven't just installed some other electrical equipment close by that could be causing interference?

 

[samwise]

Ran out of time when testing the head units and did not check through the system. I have just been down again and it looks as if the culprit was the deck plug. Evidence of unwanted greenery around a couple of the pins. Cleaned it out and WD40 applied and it seems to have done the trick.
Should have checked the plug first as I know perfectly well they are the weakest link in any boat electrics / electronics system! Thank heavens I won't have to climb the mast again!