Thanks to everyone who replied re: cabin lights wiring. I have found and
corrected the problem. After considering what everyone said and thinking
through the logic of it, I made a couple assumptions about the existing
wiring at the old fuse blocks. I assumed that only positive leads were
fused--but checked this first by putting a voltmeter on each to make
sure none were grounds. Then I determined which were not live positive
leads with the voltmeter and found the dead one. When I ran a live
positive to it, the lights came on. Somewhere there was a break in the
positive feed to that circuit. Easily fixed. Now, just to be safe (and
to learn how much current each and every electrical item on the boat
draws), I plan to put an ammeter between the battery and the main
circuit, turning on each thing one at a time to measure its draw. By
comparing these amperages to the predicted draws (from manuals for
various appliances, and the wattages of the various lights, etc.) I
should also be able to find any suspiciously high draw on any bad
circuit--to discover, for example, whether I did a poor correction of
the lights circuit. What fun! I still have a rat's nest of old wires to
clean up, but I've found almost everything now and rewired (and labeled)
all circuits to new fuse blocks and switches.
corrected the problem. After considering what everyone said and thinking
through the logic of it, I made a couple assumptions about the existing
wiring at the old fuse blocks. I assumed that only positive leads were
fused--but checked this first by putting a voltmeter on each to make
sure none were grounds. Then I determined which were not live positive
leads with the voltmeter and found the dead one. When I ran a live
positive to it, the lights came on. Somewhere there was a break in the
positive feed to that circuit. Easily fixed. Now, just to be safe (and
to learn how much current each and every electrical item on the boat
draws), I plan to put an ammeter between the battery and the main
circuit, turning on each thing one at a time to measure its draw. By
comparing these amperages to the predicted draws (from manuals for
various appliances, and the wattages of the various lights, etc.) I
should also be able to find any suspiciously high draw on any bad
circuit--to discover, for example, whether I did a poor correction of
the lights circuit. What fun! I still have a rat's nest of old wires to
clean up, but I've found almost everything now and rewired (and labeled)
all circuits to new fuse blocks and switches.