B&G VHMU Wind Angle Issues


New member
I'm hoping for a B&G wizard to chime in with advice or a fix for my wind angle issues...

I've got a J/88 with a full suite of B&G instruments including an H5000 Hercules and 810mm VMHU. I recently had the MHU refurbished in Fort Lauderdale by Wheelhouse Marketing run by Jake Marantz. They replaced the entire cable due to corrosion and the wind speed bearing. The PCB was deemed good. It checked out on their bench and as I moved the wind vane, AWA changed correctly.

When I connect to my boat, the wind angle is not correct as AWA, TWA and TWD are all off (sitting at the dock, using a spare cable). To try and troubleshoot I measured voltages at the junction box and the cable that plugs into the H5000 circuit board. I get good readings at both locations which tells me voltages are getting to the CPU.

HOWEVER, using the B&G Websocket, the voltages displayed there are not the same as read with the multimeter. Blue is zero and Red and Green are different although perhaps in the ballpark. I did this for zero and 90 degs wind angles (measured by eyeball). You can see these in the attachment. I've confirmed the source selection for Measured Wind is the MHU and the MHU alignment is 0.5 degs. I've also tried reseting the CPU numerous times, no change.

Open for suggestions before I throw it all overboard and go back to a windex and compass.

Screen Shot 2020-12-20 at 9.25.44 AM.png



New member
Sounds like a problem at the H5000, not the VMHU. The voltage tables from the mhu are available on the b&g website, but looks about right on at the junction box/cpu and there is something amiss with the cpu ADC.

Get them to check your h5000 cpu on the bench.

Or, on the 88, we often turn off the instruments as to not get distracted. Just go back to a windex :)

Also, violet is the windspeed so don't worry unless that isn't working either. You can momenterally short violet to ground at the cpu, simulating one revolution of the wind cups.



New member
Thanks, pursuing a warranty claim with B&G for the H5000 CPU. I'm told an alternative would be to get an Analog Expansion Module, plug the MHU into that and bypass the CPU connector. Agree that the instruments can be distracting but since the boat came with all this stuff, I'd like for it to be working. Violet/windspeed is okay, just included it for completeness. 



Did you look at or reset the calibration tables in the H5000? Possibly the previous owner compensated for prior poor performance with wacky calibration adjustments.



New member
Yes, reset to factory settings and no joy. Was really hoping there is some obscure setting I'm missing that is hosing things up but haven't found it. I think since the blue wire consistently shows zero volts at the WebSocket means something is amiss with the CPU.



New member
Why not replace the wind angle bearing too?   With my MHU the wind speed bearing failed only a few months after my wind angle bearing.  The failure started off as intermittent and slowly got worse.    After replacing it everything worked as normal.   It's cheap and easy to do and should probably be done anyways because you replaced the other bearing already and they might have a similar life.   https://www.bandg.com/bg/type/instrument-sensors-and-transducers/wind-sensors/mhu-angle-bearing-1c42a942/  Here is the part!  

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New member
In case anyone cares...turns out the H5000 CPU was faulty and B&G replaced it under warranty. Everything reinstalled and working correctly. Had to manually re-input my polar and calibration data because it wouldn't load the backup file from an iPad.



New member
Worked it through the dealer I bought the boat from and it was relatively painless. Saved me about $2400 (cost of a replacement). 


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