Electric problem

[marioxp]

I had a hard-to-explain phenomenon happen to me.

Both the VHF radio station and the car radio, which are on the same fuse, burned out. The negative wire from the car radio burned out completely.
Later I noticed that I had no shore power, shore power fuss had popped out, the cause was an old heater element from the water heater. I sent the VHF radio station to service and they successfully fixed it (if I understand correctly, the internal fuses were blown). I replaced the car radio because it was burned out and I replaced the heater element, now everything works.
  This wouldn't be so strange if my VHF radio station hadn't blow  two years ago (the internal fuses were blown) and water level indicator on the panel 201 hasn't worked since then.

I was never able to find the root problem.

Does anyone have an idea what could be the cause of this electrical problem.

[MagicalArmchair]

Yikes, you had a lucky escape there. It would be very hard to track that back short of tracing every wire - strange the VHF has burnt out twice. I would certainly make sure there are inline fuses to those devices that would blow before they burn out.

Those panels are hard to inspect and keep tidy as the access is not great.

[marioxp]

I forgot to mention that the negative (ground) wire burned out!

[Yngmar]

That wire failure is classic corrosion, you can even see the green bits where the copper has gone bad. That's why everyone recommends tinned wires these days and you should also apply grease to keep seawater away from connectors and crimped fittings. It does get everywhere, even when not leaking directly onto something, there is a fine airborne mist of salt spray in the boat that settles on things. If the sun shines down the hatch just right, you can sometimes see it with your bare eye.

Those connectors pictured are built for cars and not boats, they will corrode pretty fast, same reason all the Eberspächer heaters always fail. Usually the weak point is the crimp between the wire strands and the connector. Sometimes also the contact between the spring-loaded connectors. As it corrodes, it expands and conducts less well (resistance increasing). That means more power is lost as heat, increasing the current flow (the device continues to demand the same power after all, so the heat loss is in addition). More current flow means even more heat until something melts. Either the fuse, but since the fuse is sized to protect an intact wire, not a corroded one with reduced conductivity, in this case it's usually the wire or crimp that fails. Copper conducts heat very well, as you can see by the long melted plastic cover.

So replace that shoddy car wiring and when you install it new, get some silicone spray grease (sometimes mislabeled as silicone oil), €2.99 a can from Lidl and spray it into those connectors, front and back (where the wires exit). This will not hinder contact in any way but prevent that salt spray from settling on the metal and inhibit corrosion for a long time.

People used to recommend Vaseline (petroleum jelly) in the olden days, but that is outdated information.

[marioxp]

That wire failure is classic corrosion, you can even see the green bits where the copper has gone bad. That's why everyone recommends tinned wires these days and you should also apply grease to keep seawater away from connectors and crimped fittings. It does get everywhere, even when not leaking directly onto something, there is a fine airborne mist of salt spray in the boat that settles on things. If the sun shines down the hatch just right, you can sometimes see it with your bare eye.

Those connectors pictured are built for cars and not boats, they will corrode pretty fast, same reason all the Eberspächer heaters always fail. Usually the weak point is the crimp between the wire strands and the connector. Sometimes also the contact between the spring-loaded connectors. As it corrodes, it expands and conducts less well (resistance increasing). That means more power is lost as heat, increasing the current flow (the device continues to demand the same power after all, so the heat loss is in addition). More current flow means even more heat until something melts. Either the fuse, but since the fuse is sized to protect an intact wire, not a corroded one with reduced conductivity, in this case it's usually the wire or crimp that fails. Copper conducts heat very well, as you can see by the long melted plastic cover.

So replace that shoddy car wiring and when you install it new, get some silicone spray grease (sometimes mislabeled as silicone oil), €2.99 a can from Lidl and spray it into those connectors, front and back (where the wires exit). This will not hinder contact in any way but prevent that salt spray from settling on the metal and inhibit corrosion for a long time.

People used to recommend Vaseline (petroleum jelly) in the olden days, but that is outdated information.

Thank you, this advice is welcome for all electrical connections on the boat. I also have Nigrin kontakt-spray, I don't know if it protects the electrical connections.

[MagicalArmchair]

I use dielectric grease on the connections around the windlass that get hammered by waves and is periodically doused in sea weed or whatever from pulling the anchor up.

https://www.thedrive.com/maintenance-repair/39173/dielectric-grease

You don't need much... and you don't want to get it everywhere as its a monkey to clean up.

I have some pretty grim cabling for the car radio turned boat radio I should probably rip out, but then Mirage lives a very easy life with a marine dehumidifier running when I am not on the boat, so there is little or no damp down below (shows I am not doing enough actual sailing!!!!).

[sailingnut43]

Great to see that the forum is still alive!!!

If all the failures occurred at the same time, I would suspect some kind of electrical surge. Possibly via shore power connection, or lightning. If it is lightning, you will likely find more spots of charred wire insulation. Is your battery charging system, shore power charger and engine alternator working OK?