DSC radio to GPS interface problems - HELP needed!

Help! I seem to have tried just about every wire combination to link my radio and GPS together. As yet no luck. I have read about published diagrams being wrong, these are the advice from each products web site. Can anyone tell me for certain which wire on the GPS to connect the 2 from the radio for full DSC data connection – both ways????

Navman 7100 radio wiring:
Connecting VHF 7100, 7200 to a GPS
NMEA OUTPUT + from third party instrument, connect to yellow wire (NMEA IN) on NAVMAN VHF7100
NMEA Output – from third party instrument, connect to Green (NMEA -) on Navman VHF7100

Garmin 178C wiring;
Black – Ground power/data (-)
Blue – Port 1, Data out (tx+)
Brown – Port 1, Data in (rx+)
White – Port 2, Data in (tx+)
Green – Port 2, data out rx+)

Many thanks for any advice given.

My Navman fuel computer had the colours marked wrong so it is quite possible you have the same problem. Just swap the + and - nmea wires around - only the signal wires - it shouldn't hurt.

thanks for the advice. i will keep trying. I might be having problems with the common ground, i think.

Can anyone tell me for certain which wire on the GPS to connect the 2 from the radio for full DSC data connection – both ways????With only two wires you can't have a two way connection. So, if your info above is complete, the following should be correct.

If your Navman cable colours are correct then; Garmin blue to Navman yellow, Garmin black to Navman green.

You could use Garmin port 2 if you prefer then; Garmin green to Navman yellow, Garmin black to Navman green.

If Codders is correct for your case then the Navman cables will need to be reversed.

blue out from garmin to yellow in on navman, and the green on the navman to
a common earth such as buz bar.on the 7100 there is no data output from the radio to an external device, only data in to give gps position.

as jw:thumbs:

Many thanks to you all, seems clearer now. I will print out your advice and try again this evening. Thanks again.

All working well after your excellent advice.

Many thanks.