GP32 nmea output issue

[Aqua_vitae]

I use a GP32 on my sailing boat. Its NMEA output is connected to a VHF radio, an autopilot FAP 511, a repeater RD30 and a computer RS232 port. All this have been working fine for more than 12 years.
Since few days I experiment a small issue related to NMEA output : the GP32 randomly stops sending for few minutes VTG and GGA sentences (not at the same time for these 2 sentences) BUT NEVER stops sending the GGL sentence.
I can see this issue on the computer which looses SOG and COG on the chartplotter display, and sometimes on the autopilot which alarms : "no speed information". When this issue happens the GP32 (and also RD30) continues displaying SOG and COG without any problem.
Any idea on what happens ?
Regards,
JF.

 

[TheReaper]

NMEA0183 standard is output from one talker can go to a maximum of 3 devices. When adding a VHF...that counts as 2 of the 3. If only the wht & blu wires were used for all these devices, the NMEA port probably died. If the first three were using the wht & blu wires and the computer was using the blu, yel & grn wires also...that was never supported by the GP32 because the ground cannot be shared by RS422 and RS232 at the same time. With that type of output need, we would have recommended using a NMEA expander box so as not to overload the output on the GP32 itself.
Bottom line: The GP32's output is very likely dead and there is no repair capability on those. The replacement would be a GP39. With all of those outputs, the GP39 will need a NMEA expander box to support all of the devices being connected. Some even come with a true RS232 output for a computer. Here's a link to one company that I know makes them: https://nolandeng.com/

 

[Aqua_vitae]

Thank you for your reply.
My computer is actually connected via RS232 (blue, yellow, green wires).
I would have been happy to find in GP32 documentation the NMEA standard of output you speak of:
. maximum of 3 receiver devices connected to one sender,
. vhf radio acts as 2 devices,
. RS232 and RS422 cannot be used at the same time.
Probably you are right the NMEA port is died. But it is difficult for me to think that a died port never fail sending GGL and fail (sometimes) sending GGA and VTG.

 

[TheReaper]

I guess the point is that the wiring is incorrect as it stands now. It may have worked perfectly for time, but as you have said, it has started working intermittently. Since it's still working at all, I recommend disconnecting the RS232 output (blu/yel/grn wires) and the connection to the VHF radio and see if it stabilizes. If it does, then it's recommended to get the NMEA expander and make all of the appropriate connections through it.