Alternator interrupt Blue Sea switch

[skipgundlach]

So, on the recommendation of my marine electrician who surveyed my installation as I was accepting the fact that my less-than-3-year-old battery bank (see "Battery Woes" series) had died, I swapped out my 1-2-both-off Blue Sea switch for their 'smart' switch which has only off-house-emergency/start positions.

The posts make it such that the alternator always charges the start (in my case, both start and windlass, run through an isolator) battery, and whatever charge sources you may have do the house bank. Putting it to 'emergency/start' combines the circuits.

My old switch had an alternator interrupt pair of screw terminals. I have currently replaced that switch with the new one (and all new cables; more on that when I've finished and will update the BWoes series), but have left the alternator pair attached to the old switch, turned to the 'both' position.

With that as background...

Previously, a high-rev initial start would kick in my tachometer; it previously had a power-to-the-alternator line which made it active all the time, but those have not been used for some years now.

With my old switch in the 'both' position (only affecting that line to/from the alternator), to maintain the condition which was present before, I started the engine to move it to the dock position most favorable for hoisting our L16 batteries aboard (and the old ones off). No tach. I'd had some tach anomalies recently (wavering level despite constant revs audibly), which make me wonder if I have an alternator or a connection issue.

And, I assume the proper solution for this particular light wire will be to remove the ring connectors and butt-splice those together. The new switch cautions not to turn the switch to "off" while the engine's running, but I note that the old switch had that warning as well.

So:

What does that circuit actually do,

and,

Is that the likely source of my tachometer non-start and/or prior anomalies? And if so, how do I cure it other than swapping in one of my spares and taking it off for rebuild?

Thanks.

L8R

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[CarlF]

Turn off the new Blue Sea switch and hit your thruster for 5 seconds to slightly discharge your battery and see if the tach comes back.

If so, this is the standard problem of tachs that pick up their signal from the alternator (most Yanmars). If the batteries are completely charged, the tach can drop out. In this case, I bet your house bank (with possibly other charging sources - solar?) have a high enough voltage to confuse the regulator.

Some Balmar regulators have a special provision to keep the tach signal alive. In my experience, it doesn't always work.

If you have solar or wind, you might disconnect them too and see if that fixes the problem too.

[skipgundlach]

Originally Posted by CarlF

Turn off the new Blue Sea switch and hit your thruster for 5 seconds to slightly discharge your battery and see if the tach comes back.

If so, this is the standard problem of tachs that pick up their signal from the alternator (most Yanmars). If the batteries are completely charged, the tach can drop out. In this case, I bet your house bank (with possibly other charging sources - solar?) have a high enough voltage to confuse the regulator.

Some Balmar regulators have a special provision to keep the tach signal alive. In my experience, it doesn't always work.

If you have solar or wind, you might disconnect them too and see if that fixes the problem too.

Did you mean to say 'old' switch? That would (guessing) open that circuit.

As to fully charged, we often would exceed that measure if we had to motor a long way, so I don't know that high voltage or power would negatively impact my tach...

L8R

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