Thursday, June 16, 2011

Lessons in Electrical Trouble-Shooting

  1. Never assume there is only one fault, even if the problem is new.
  2. Never assume the previous owner didn't set you up. He did.
  3. Always start with the multi-meter.
  4. Always trace the wiring.
I travel altogether to much in my work, but there is a silver lining, beyond meeting good people and sometimes going interesting places; the boat is "sort of" on the way to the airport. Often I can manage a little time and get some hours and a night on the boat, though not always sailing time. Still, I'll take it. Projects that might subtract from sailing time get done and quiet time at the marina is bliss.

My last stay, as I turned in for the night I realized the reading light and fan didn't work in either cabin, and neither did one of the cockpit lights. Since my solar panel project had passed through both of those boxes and only those boxes, it seemed clear I had made some error that I could track down in the morning.

My multimeter battery was dead and I was too lazy to look for a replacement. I opened the cockpit light but found no obvious fault. Not surprising, since I had not disturbed any wires there. Then I dropped the ceiling on the starboard side. When I dropped the ceiling for the solar project the wires leading to the ceiling fixture had flown apart; the PO had done some stupid wring-size crimp connector splicing and everything came apart. I had right-size spliced it back together, but I had certainly guessed on some of the connections; there seemed to be an obvious pattern, I had used my meter, and I thought it was right... but I couldn't remember it I had tested the reading lights (I retrospect, I remember that I did). I tugged at all of the wires; tight and solid.

So I chased down a battery for the multi-meter. I had one on the boat, right where it was supposed to be and had the meter working in minutes. I should have done that first.

I checked the cockpit light. Power in, power on the pass-through. Clearly a bad switch. Since I picked up an unused spare at a marine consignment store for $3.00 a year earlier, a simple fix. It had been acting up and I should have figured as much, rather than place blame on the solar project. Easy. Two crimps and two screws.

 Lesson one: Start with a multi-meter. I checked the power on the starboard ceiling fixtures; no faults. Huh. It seemed the solar project was not involved. I traced the feed to the cabin lights. Sure enough they are separate from and unrelated to any other circuit (though there are many lights and fans on the "cabin light" breaker, the breaker feeds a pair of terminal strips and the aft cabin reading lights and fans run off a single feed from those strips. A mental light came on; we had a birthday party the week before with a group of teen age girls (my daughter is 16 now!) and as a result we had stuffed an unusual number of PFDs in the stern lockers... right where the cabin lights branch apart.

Proper wiring tools are essential

And sure enough, the PO had added fans and in the process, used crimp connectors. I'm a strong believer in crimps; I did hundreds for a 1-year hyper-saline salt chamber torture test for Practical Sailor Magazine, without a single failure. But the PO apparently either used a cheap tool or did not reset the tool for the fittings he used. In fact, the fittings were so far below standard size, that the die in my ratchet crimper for 2 gauges smaller fit perfectly; it should not have closed at all on that setting with that wire gauge. The wire had easily pulled out, without any damage, but remained hidden from view inside wire loom.

Problem solved for a few pennies... and at least 30 minutes of wasted diagnostic time because I was not systematic. Well, I knew better, now the lesson is further reinforced, my multimeter has a new battery, and now you know better as well.

 Lesson two: Never let your daughter count candles for your 50th birthday cake.

1 comment:

  1. I have often lamented how the guy who is scared to death of his house wiring suddenly becomes qualified as a marine electrician as soon as he steps aboard.

    Nice candles.

    s/v Eolian