Further to what Neil just said, In a nutshell, if your alternator is not connected to anything at all while spinning it will be impossible to regulate its output voltage (as the electricity it is generating has nowhere to go) so may spike it's internal voltage as high as several hundred (or more) volts, even if that is only for a few milliseconds, but that is enough for the internal rectifying diodes to fry, and perhaps for the windings to short internally, permanently toasting your alternator.
Ken H. On Sat, 21 Jun 2025 at 12:26, Neil Gallagher via CnC-List < cnc-list@cnc-list.com> wrote: > Nick, > > If the voltage sensing line on the alternator is disconnected, that can > lead to the alternator (via the voltage regulator) putting out high > voltage and damage can occur from overheating. Not sure why someone > would put a switch in this wire if that's what it is, as you would never > want to run without it. > > Neil Gallagher > Weatherly, 35-1 > Glen Cove, NY > > On 6/20/2025 11:56 PM, Floersch.net via CnC-List wrote: > > Hi folks! > > > > Our CNC ’34 from 1978 … has an Atomic 4 engine. > > > > Last summer we finally installed solar panels! What a relief! Before > that the only way the battery charged was via the alternator. > > > > Now our battery is always (basically) getting charged… even if we do not > use the boat for a week. > > > > Cool. > > > > So the question is this… the previous owner told us that we MUST turn on > these "various switches" to enable the alternator charger system prior to > using the engine. The vague statement was along the lines of “if you do not > flip on the switches, then the alternator won’t charge the batteries, and > ‘it’ will burn out.” > > > > We are not sure what “it” is or if this makes any sense. I can > understand, kinda, if the alternator is generating electricity and has no > sink to dump it into… maybe that is bad. But a battery is not an unlimited > sink for the energy, so I can’t imagine how flipping the switches saves > from burn-out of some component. > > > > Does anyone else have some sort of switch or set of switches that must > be turned on before you start the motor to make sure your alternator is > happy? Or did we misunderstand the previous owner? > > > > (Yes I realize there is a lot f vagueness to this… but perhaps it will > make sense to someone, so I’m putting it out there to see what you throw > back at me :) > > > > Nick in Vermont > > Your contributions help pay the fees associated with this list and help > to keep it active. Please help by making a small contribution using PayPal > at: https://www.paypal.com/paypalme/stumurray All contributions are > greatly appreciated. > Your contributions help pay the fees associated with this list and help to > keep it active. Please help by making a small contribution using PayPal > at: https://www.paypal.com/paypalme/stumurray All contributions are > greatly appreciated.
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