Too High Voltage Issue on Garmin 740S Chart Plotter

[vector420]

Very strange issue. We're all stumped here on the dock. If anybody can help that would be greatly appreciated.

PROBLEM: Unit newly displays "Voltage too high! Shutting down in 5s" Then shuts down.

INFO:
-Unit Voltage (from display) indicates about 34V just before shutting down
-Voltmeter readings at/are:
Unit Plug (power pins) = 13.8v
Power Junction box = 13.8v
Batteries = 13.8v
-Unit is rated to function 10v-32v
-Unit voltage (from display) increases slowly from 13.8v to 34V (eventually shutting off) as engine runs but voltages at other points (incl. plug into unit) remain at 13.8v.
-Voltages at all other plug pins are less than 5v
-Nothing else is connected to unit (No NMEA, no depth sounder, etc.)


FAILED ATTEMPTED FIXES:
Reset to Factory Settings
Remove chart SD card
Change electrical ground from battery ground to RF ground

[transmitterdan]

Probably the internal analog to digital converter has failed. Could be the reference voltage generator is Zero making the converter think the voltage is at max full scale. Most likely it needs a trip to the factory for repair.

[senormechanico]

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