Short circuit interior lights

Before I can advise you need to clarify if this is a SHORT circuit or an OPEN circuit. Sometimes these term are used interchangeably. They are very different conditions!  

Update: Without any intervention on my side, the short circuit seems to have “auto-repaired.” One morning it was simply gone and the lights started working normally again. Unfortunately, this has happened before, so I don’t consider the issue resolved.

Once the circuit came back, I tried tapping on every panel/door/cabinet on the port side and shaking cables to see if I could reproduce the short and narrow down its location. No luck—nothing I did triggered it.

The only difference I can think of is temperature. I had been heating the boat with the Webasto and left the water heater on for a couple of days. Maybe the warmth caused something to expand/shift (a wire, connector, or screw) and the short disappeared.

In any case, I’d really appreciate help identifying the cable routing on this circuit and the locations of any junction boxes/connectors I should check.

On my 370, which is one of the very early ones, I had a problem in rough conditions with taking water in through the swan neck at the base of the lights. This caused the trip for the port side to trip as water around the forward port bulkhead light short out. I ended up having to rewire, change the switch and bulb holder in light unit to fix the fault. As Mark says, it might be worth having a look in this area. There’s a thin ceiling panel that runs across the top of the bulkhead in the fore cabin that the wire drops down from to the light.