Join Date: Dec 2004
Thanked 57 Times in 57 Posts
Rep Power: 13
Some good advice in the previous posts...
For safety's sake, kill any 110V power coming aboard...unplug SP, shutdown generator.
Your fridge is likely on its own circuit, since it is a relatively large load.
Other 12V circuits through your distribution panel are likely powered on the positive side from a single high capacity wire from the battery selector switch. House battery positive leads (normally red) are individually connected to the battery selector switch. If you have no power from either house battery in any switch position, and if the problem is in the positive side of the wiring, it is either the switch or the wire from the switch to your distribution center (it is unlikely that that wire is fused...usually only the individual loads are breakered/fused.
The negative side of the power distribution to these loads (normally black wires) is generally wired to a terminal block outside the panel on a bulkhead somewhere. The negative leads from loads go to this terminal block which is in turn connected via a large ground wire to ship's ground. If this large ground wire fails, all the loads off the ground terminal block will fail since there is no return circuit for the power to the batteries.
So, check battery voltage using installed voltmeter with the battery selector switched to 1, 2, and both, or handheld voltmeter at the batteries. If voltage is good at the installed voltmeter, and the voltmeter is at the distribution panel, open the distribution panel and check for voltage at individual loads' breakers. If you have voltage, the problem is on the negative side. If there is no voltage at the panel, gain access to the back of the battery selector switch, identify the output terminals for each position, and check voltage. If there is no voltage, the switch is bad. If there is voltage, check the voltage at the panel breakers, and if there is no voltage there, the main lead to the panel is likely at fault (open).
If there is voltage at the distribution panel breakers, your problem is on the negative side. Check connections from the battery negative to your house ground, and from the house ground (could be at the engine) to the negative terminal board. Use an ohm meter to check electrical continuity of the circuit, as well as visually inspect.
Wiggle wires a bit looking for broken wires, look for corrosion (green from copper wires or white at battery connections) and clean any dirty, corroded connections.
Hope this helps. Good luck.