GPS Freezing

[Sakura]

I got strange problem with GPS. While motoring, after an hour or so my GPS freaks out. The set is: GPS: Evermore SA-920 (rs232), connected to Navicom rt-650 VHF. After sometime on the motor it starts to show some bizzare characters in place where long/lat/SOG/COG shoud be. Switching the VHF off and on, then NO GPS INFORMATION show up. Sometime it starts working for few seconds then freaks out again. It looks like it happens only during motoring, and only after and hour or so since starting the engine. The GPS cable goes through engine compartment but slight amount of heat shouldn't affect it at all. Has anyone had similar problem?

[Viking Sailor]

My guess is that your charging system is putting out more voltage then the GPS can handle. This could be do to a bad or incorrectly adjusted regulator. The reason that it take a hour before the GPS quits is because in that hour the batteries are being charged which causes the voltage to be low enough for the GPS to work. You can check this by switching off the charger and see if the GPS starts working again. Also, you can measure the charging voltage. If voltage is above what is recommend for the type of batteries you have that is a real problem for both the GPS and the batteries.

[ActiveCaptain]

I'd hunt around the ground wire for the GPS and see if it is on a different ground than the VHF.

[Sakura]

Interesting idea with high voltage, haven't thought of that. Usually at fully charged batteries with motor on it's around 14.1V, with motor off 13.8V Gonna have check this one then. As for the gorund - NMEA ground is the same as in VHF, and GPS is drawing power from same wire with VHF - therefore same ground here as well.
Cheers