Hi, I'd check the battery and alternator connections carefully. And the main switches, too. If the batteries get disconnected while the motor is on, the alternator will create a load dump that can be even over 100V for a fraction of a second. In principle, automotive and marine electronics should be protected from that but you never know. I'm only speculating, but if that was the reason, maybe the voltage spike was short enough that the fuses didn't have time to heat up?
Google for "load dump" if you want to learn more. Cheers, Matti Airas C&C 36 "Hurma" Helsinki, Finland On Thu, 26 Sep 2019 at 22:26, Ian Matthew via CnC-List < cnc-list@cnc-list.com> wrote: > I have been following the list for many years and I enjoy reading the > wisdom of this group. I have an interesting problem and seek your advice. > > I have an very intermittent electrical problem (in fact it has only > happened twice in the last 7 years. In both cases it has resulted in > electrical / electronic components becoming 'blown out' with all fuses > inline remaining good. > > The first time I suddenly lost my AM/FM radio and ALL my navigation > lights. The engine also stopped as I had no power to drive the electric > fuel pump. This happened when motoring back home at night after a long > race. Fortunately there was wind and a hand-held VHF and a powerful > spotlight on the sails allowed us to be seen by commercial traffic. > Afterwards, I checked - ALL the incandescent bulbs that were on had blown, > but the fuses were OK. The radio had internal circuit board components > blown but again the inline fuses (there are 2) were OK. In the case of the > fuel pump, this had to be replaced. > Thinking this may have been a spike from the alternator, I replaced the > alternator. > > Last week (3 years later), motoring back in the dark I had a similar > problem, but this time only my VHF radio 'blew'. Again the inline fuse was > good. The navigation lights have been replaced with LED lights and the > AM/FM radio was off. > > I often motor after long races and this has only happened twice! > > Does anyone have any ideas as to what may have caused this. I am an > engineer so can diagnose most things but this has baffled me. > > I am about to upgrade my VHF radio for one with DSC and internal GPS and > to add some wind instruments. (I have a Raymarine knotmeter/depth meter > combined, and a EV-100 autopilot.) I want to separate my electronics > electrical input and have considered putting them on an isolated battery, > but charging is a problem. Is there some circuit protector I can put in > place to stop this happening again? > > All suggestions welcomed. > > BTW - for those of you with 29 mk 1's - you can race them competitively in > strong winds (as is usual on San Francisco Bay) - keep the boat flat and > have a really good crew! > > > -- > Ian Matthew > "Siento el Viento" C&C 29-1 > San Francisco Bay > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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