Forums, Electrical Systems, Navigation and Safety equipment, Gremlins!

Tazling at 10/08/2013 20:34:09
Last night — or in the wee hours of the morning rather — my buddy boater woke me up (we were rafted in Frances Bay BC, for those who know where that is, and Johnstone Strait was honkin’ westerly, 35 kts) with the dreaded conversation opener, “Wake up, I think we might be dragging.” To leeward of us, instead of empty space, was an old log boom: not the kind of thing you want to get tangled up with at 2AM. OK, time to put some warmer clothes on and peel off, maybe go set someplace else individually.

Only problem with this already rather annoying scenario was that when I went to start the engine, absolutely nothing happened. No solenoid click even. The instrument panel lights dimmed slightly when the starter was depressed, that’s all. Yikes. Whitecaps all around and boomsticks behind us and no engine. [SKIP TO “QUESTION” BELOW IF YOU DON’T CARE TO READ GORY ANECDOTAL DETAILS.]

Rapid sanity checking revealed that all 3 batteries (2 house 1 engine) were all a bit lower than expected - 12.5vdc, which should in theory be enough but evidently wasn’t. We had motored all the way up there (the wind didn’t start up till after sundown in the channels and we were already late for the tide) for more than 3 hours, so they should have been all charged up. Jumper cables quickly hauled out to connect the engine starter battery directly, bypassing all boat wiring, to house battery #2 for added oomph. Yay, engine starts. BUT… no sign that the alternator is actually charging anything, no elevation of battery surface voltage. So, I cuss and fume and figure my alternator, for mysterious reasons, is toast. (And before you ask, no, I didn’t fool with the master A/B switch while the engine was running, I wasn’t born yesterday :))

As a bewildering aside, the way my boat is wired, the A/B switch does the same job as the jumper cable: when set to ALL it connects all three batteries for maximum oomph, and the start motor is fed off the hot side of the A/B switch. When these attempts were made, the A/B switch was set to ALL. So there should have been no advantage to the jumper cable, and yet it seemed to solve the immediate problem. [Yes, later on I inspected the back of the A/B switch and found nothing suspicious looking. Gnashing of teeth.]

Figuring I may not be able to get it started again, after asking for a big jolt from the apparently non-charging pack, I didn’t want to shut it off (in case the dragging issue continued) and decided to leave (at about 3AM, after considerable discussion). Navigated by hand-held GPS in fairly dense darkness through the fjords, then dawn reveals landforms and it’s just routine travelling (except for fuming with frustration at having our cruise interrupted). Arrive at the home port about 0630 and instead of turning in, feel compelled to investigate the b——y batteries one more time.

Much to my bogglement, battery 1 (which was selected while en route) and starter battery are all topped up at 13.5vdc. Batt 2 which was not selected is still at 12.5. So umm, clearly, the alternator while travelling was charging correctly. Much head scratching and eliminating of variables: if it is charging OK, then how did we arrive at Frances with low voltage and unable to start the engine, after almost exactly the same number of motoring hours?

Much fussing over every connector, finding some stuff a little loose that “shouldn’t” (oh how I love that word) make any difference. More head scratching. Unable to reproduce problem. Unable to come up with a convincing theory.

QUESTION: So — at long last — knowing that no one can comment meaningfully on an unknown wiring buss, my question for the forum is just this: has anyone, anywhere, at any time, ever seen an alternator go flaky rather than fail hard? I personally have not. I have known them to stop working outright (blown diode), or to undercharge under certain conditions (loose belt for one); but I have not known one to fail — apparently entirely — for a period of hours, then work perfectly a few hours later. I would like to eliminate the alternator from my list of suspects. [BTW, I checked the belt tension. It was perfect.]

If anyone here loves and understands alternators and would like to expand my folk-knowledge of the range and complexity of their failure modes, I’d be grateful. Otherwise I’m left blaming the gremlins and suspecting the alt for lack of a better theory, which is far from satisfying.

BTW, night running turned out to be anxiety-inducing (we do have dead trees floating around in our local waters here and there) but stunningly beautiful: sky full of stars, Perseid meteor shower just beginning, tiny whitecaps building and glowing with bioluminescence on jet black water; land forms looming up featureless as black paper cutouts. Unforgettable despite the lurking paranoia about “finding something” along the way.

I do so loathe and despise intermittent failures.

Keith Feltham at 11/08/2013 10:09:48
I am the worlds worst expert when it comes to electrics but simply by ellimination it would appear that Bat 2 is your problem. It was eliminated from the equation on your trip home, when things worked OK. My goes is that you have a direct short in Bat 2 that is drawing off all the charging current and drawing down the other battery.

Tazling at 18/08/2013 05:55:57
Actually, in the sober light of several subsequent mornings, it seems that there are two problems: one was the traditional loose wire (aha!) — didn’t seem loose to a casual inspection but a closer, less hurried look found a wingnut suspiciously loose. Seems that clamping the jumper cables on may have squeezed it into adequate contact with the batt terminal, or that is our best guess here.

The other issue is that batt 2 is weak, and the reason for that is a bit boring to go into here - the way the batteries were wired to the solar panel and the distrib panel by PO is a bit “creative” and not what I expected :) At any rate, it has been starved of solar charge as a result and I believe it drags the other batteries done when they are ganged in the ALL position.

Ah, the little surprises you discover when you take over a 30 year old boat! sort of like an Easter Egg Hunt except that some of the eggs are a bit on the rotten side :-) I’ve just discovered (in some heavy weather recently) that my foredeck hatch leaks when you take green water over the bow. Ugh.

Alan Dixon at 01/09/2013 08:59:55
I has an intermittent fault with the starting 3 years ago, 12 volts + at solenoid but no start, eventually traced back to the Isolator switch, 28 years of small arcs meant the amps could not get through. changed the switch and no further problems.