Unwanted Dimming

QuestionI have a 2000 Rinker Fiesta Vee 310. My trouble is the cabin lights. The lights will shut off momentarily when we are using one or more of them, and whenever we use the freshwater pump the lights will shut off the same way. Whenever we anchor out, the lights will die in a short while. I am looking for possible solutions.

– Frank Ball, via BoatingWorld.com

AnswerLots of possibilities! My initial thought would be that it sounds like a bad/intermittent ground or loose connection, but more info would be helpful. Such as, what type of lights (incandescent, LED, etc.), and when the lights die out at anchor, does that mean the battery is dead or that the lights just go out (I’d assume the latter, but who knows)? A weak or borderline battery would also exhibit many of the same symptoms. The lights may look OK at first, but when the pump kicks in the larger draw would make them dim (something that would be easy to note visibly) or even go out. Keying the VHF would likely cause the same symptoms, although they’d probably use the water pump more at anchor than the VHF, making it more noticeable. For “hot” lights that draw a lot of power, the more you have on, the quicker a weak battery would dip under proper operating voltage, causing them to dim or go out. This, of course, would not be as noticeable (or even occur) as long as the engine is running and the battery is being charged by the alternator.

I’d probably start by testing the battery(s) while under load to see if they are up to snuff.


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