No Power to dash on battery one or two but power with both

mswilkfl1

Power to dash when battery selector switch is on both but no power on dash when only one or two is selected.  I have a 2005 GS202.  Battery 2 is charging (only)7.5volts other is 12.5 volts. I did have the 4amp fuse blown at the battery and the 30 amp fuses are good.  Is there a a device at the switch that could be bad?

M99

Its hard to say because with your battery voltage so low, that alone could cause what you describe. Once both batteries are fully charged, meaning around 13V at each, then see of its the same.  If so, I'd guess that someone mis-wired the battery switch.

Ernest_T

Sounds like you have one bad battery.  A fully charged healthy battery should read around 12.7 volts at 100% charge.  12.5 volts indicates a 90% charge.  Anything below 12.0 volts is less than 50% charged.  7.5 volts would indicate one or more bad cells.

There are different wiring possibilities, depending on what type of switch and setup you have on your boat.  I'd suspect your switch is wired wrong or you have a bad switch in addition to the bad battery, or possibly both batteries are going bad.

First step would be to load test both batteries and go from there.