[C320-list] Instruments gone awry

[Graeme Clark]

On instrumentation its is good practice to only have the instrumentation ground circuit connected to boat ground in one single place

Otherwise you can get ground loops where slight variations in ground voltage at different parts of the boat (nominally zero) set up micro currents that can upset instruments designed to read micro currents!

Graeme
1996, #366. 
Sent from mobile: please excuse typos etc.!


> On 13 Jun 2019, at 18:31, Dave Chase <londoc at blackbury.com> wrote:
> 
> Since there are a number of problems, I'd look at power/ground connection issues and check for corrosion. Have any electrical connections been changed such that a ground may have been moved?
> 
> Dave Chase
> Indigo
> 1994 C320 #97
> 
> 
>> On 6/13/19 12:21 PM, William Russell wrote:
>> On my 1998 C320 (#545) I have ST40 Plus instruments (speed, wind, depth,
>> autopilot).  They've always worked fine in previous years.  This year, I'm
>> getting very unreliable (or non-existent) performance from them.  Speed
>> seems to work, but I've not checked it against a GPS to see how accurate it
>> is.  Wind direction doesn't work at all, until partly through a race it
>> starts to read, though not consistently or accurately compared to the
>> Windex.  Wind speed reads, but again, I can't tell how accurately, and it
>> often seems way off. Depth is completely inaccurate - sitting at the dock
>> in 6-7 feet of water, it showed 14-16 feet, and changed minute by minute
>> even though we weren't moving.  The compass on the autopilot reads 20-30
>> degrees differently than the binnacle compass, and the "wind" setting on
>> the autopilot won't work without an accurate apparent wind direction.
>> I can't figure why I would get such variable and unreliable performance
>> from all of the instruments at once.  They were installed by the (very
>> knowledgeable) previous owner, so I don't really know where to start to
>> troubleshoot.
>> Any suggestions?
>> Bill Russell
>> "Little Wing," 1998 C320, #545
>> Cayuga Lake
>> Ithaca, NY
>> 
>>