Wind instrument malfunction

[Bill Plaia]

I have a problem with my wind instrument and I70 that I am having trouble analyzing. My wind indicator is intermittent at best and is at the moment non-functional. Both wind direction and speed are affected, but sometimes one function will be working and not the other. The masthead is connected at the base of the mast through a Raymarine junction box. Voltages at that Junction box are 7.91 for the supply, 3.xx for the port and starboard. It seems to be balanced at about 3.7 when the wind indicator is pointed straight ahead. As I anchor sail a bit one side will drop to the low 3's and the other side increases to about 4. This seems symmetrical on either side of directly into the wind. I'm doing these tests at anchor so I'm limited about how far off of directly into the wind I can get. The speed voltage is in the range of 1.95-2.4 and varies positively with gusts. With the exception of the supply voltage being .09V below the 8V spec, the mast head unit seems to be behaving as I would expect. Am I wrong?

The masthead unit is connected to an iTC-5 which is connected to the I70 through the Seatalkng bus. The Seatalkng bus is powered by the autopilot ACU200. Diagnostics on the I70 reports the bus voltage as 12.1. The I70 diagnostics see the iTC-5 and the setup program sees a wind instrument, a depth transducer, and the fluxgate compass, even when the wind display is not indicating any speed or direction pointer. The Seatalkng bus has an EV1 course head, a C97 Chartplotter, and a Seatalk-Seatalkng converter. There is a Raymarine 120 GPS plugged into the yellow port on the converter. There is also an NMEA2000 analog-nmea2000 engine converter plugged into a Seatalk port on the converter. The problems with the wind instrument predate the installation of the NMEA2000 device which is recent. For diagnostic purposes I have disconnected the entire Seatalk-Seatalkng converter from the Seatalkng bus and terminated it properly. It made no difference in the wind instrument behavior.

The entire package of instrumentation was installed in early July of 2015. I have powered down the entire boat with the exception of the ACU200, the I70, and the ITC5 and it made no difference in the behavior of the wind indication. With everything on the bus powered up all Seatalkng and the Seatalk GPS are displayed perfectly normaly with no data anomalies. Only the wind indication is a problem. The first time it happened was exiting the East River in New York near City Island. The wind speed suddenly started varying from near 0 to 70+ knots even though it was obvious that no such thing was going on in real life. We stayed in Port Washington on the south side of the river and the wind speed indication was erratic the whole time. When we got about 3 miles East of there the wind readings returned to normal and stayed that way all the way to Maine and back. Again when we got within 3 miles of the entrance too the east river on the return trip the problem returned and when we got well on the other side the readings returned to normal. There is a very powerful radio station at the entrance to the east river (WCBS New York) and I assumed that it was causing problems with the wind readings. The readings remained normal throughout our return southward and remained normal after an upgrade to the lighthouse 15.59 software package. When we reached Marathon Florida at Boot Key harbor we again lost our wind reading. Both wind speed and direction this time. The VOA radio transmitter to Cuba is located on the entrance to boot key harbor. We left Boot key Harbor for a couple of days and readings returned to normal. When we returned to Boot Key harbor we again lost wind speed and direction. When we left Boot key harbor again returned to normal roughly 3-4 miles from the VOA transmitter. These readings remained normal until we approached Nixon Harbor at South Bimini Island in the Bahamas. Wind speed would often sit at 0.0 even though the cups were spinning rapidly and wind direction seemed to be any direction but the one in which the wind vane was pointed. When we left Nixon's harbor for North Bimini the readings returned to normal. Two days later when passing through Nixon's harbor again the readings became erratic. When we got about 3-4 miles south of Nixon's harbor the readings returned to normal. I could not identify a radio tower near Nixon's harbor but was pretty convinced by now that I was getting some geographically based electrical interference and suspected radio emissions. If you can think of any repeatable geographically based sources of interference I would be happy to hear them. The system functioned normally for a week until we reached Fresh Creek on Andros Island in the Bahamas. There was a Bahamas Telephone company tower about ½ mile from us and the microwave dishes were pointed directly at us. Fresh Creek is also the home of the US Navy Atlantic Undersea Test and Evaluation Center. There is no telling what kind of radio emissions they might put out. Again when leaving that area we got about 4 miles away and all readings returned to normal. They remained normal until we approached Staniel Cay in the Exumas (1 week) when we lost both speed and direction. With the wind howling at 20-25 knots the wind speed sat dependably on 0.0 and the direction varied from occasionally indicating the correct direction to the directional indicator needle disappearing completely. I have moved to Georgetown Great Exuma and the unit has not functioned since approaching Staniel Cay 5 days ago. Most of the time the wind speed sits on 0.0 but occasionally jumps up into the 15 knot range but varies wildly. The wind direction indicator sometimes disappears completely and other times is spinning around the dial though the wind vane is clearly not doing the same. Sometimes the indicator “needle” simply disappears completely. Even when this is the case the I70 transducer setup screen still sees a wind instrument. Sometimes the wind direction is frozen in a particular direction, at other times moving but in any direction but the way the wind vane is pointing. This is a notoriously radio quiet area except for all the boats. There is a Bahamas defense force base about 3 miles from here which could be a radio source, though Because I was 5 + miles from any island between here and Staniel Cay I am starting to doubt my radio interference theory.

Before you ask, yes power has been removed from everything many times.


I am now at a loss as to whether I should suspect the I70 or the iTC-5. Please help me diagnose this.