Blowing fuses etc

[Bosunof]

The symptoms:
1. After sailing and then needing the engine, after starting the starboard lighting circuit fuse has blown (15 amps!!??)
2. At the same time the chartplotter, on a different circuit, goes off line.
3. Batteries still charge and nothing else seems amiss.

Current advice (sorrry for the pun) goes two ways. Either there needs to be suppressors in the circuit, or the regulator in the alternator is kaput.

Have you any other suggestions and remedies, please?

At present I overcome the problems by taking a log reading, switching off, starting the engine and restarting chartplotter again and a pocketful of replacement fuses.

Bosunof

 

[Guest]

Could be overvoltage or under voltage.

It all depends on what is powered at the time. For example lights in an overvoltage situation will take more current and blow fuses, if it is marginal.

However newer style equipment have voltage stabilization on the input. If you drop the voltage to say 9v during starting, the electronics will try to extract the same power and so the current consumption would have to go up.

The reason electronics shut down can be due to either but I would suspect undervoltage as a starting point.

Even 12v stabilized Halogen supplies will take more current in low voltage situations.

 

[orizaba]

sounds like a bad connection re the chartplotter fuse holder etc and live wire earthing out,maybe due to engine vibration etc,re fuse blowingi would have thought that overvoltage is most unlikely to blow a fuse,

 

[William_H]

My guess is that due to a bad connection in the starter or possibly the charging circuit some of the current is flowing through fuse.

Suggest clean and check all the heavy wire connections especially the earths. good luck olewill

 

[cliff]

[ QUOTE ]
The symptoms:
1. After sailing and then needing the engine, after starting the starboard lighting circuit fuse has blown (15 amps!!??)
2. At the same time the chartplotter, on a different circuit, goes off line.
3. Batteries still charge and nothing else seems amiss.

[/ QUOTE ]O.K. - step by step - first, to blow a fuse means you have drawn a higher current through the fuse than what it is rated for so to blow a 15 amp fuse you have drawn more than 15amps. Now comes the hard bit - why are you drawing 15+ amps through the starboard lighting circuit on starting the engine? has there been any rewiring recently? Does a new fuse blow when the engine is running?, does a new fuse blow when cranking the engine over to start? What else apart from lights is fused through the starboard lighting fuse?.

Sounds to me there has been some "modifications" to the wiring and you are drawing power through that fuse during starting.

Have you metered from the circuit side of the fuse holder to the negative bus? with all the lights off there should be no continuity.

Is it possible someone has taken a tapping off that circuit for heater plugs?.

When exactly does the fuse blow? on switching on the "ignition" or on cranking the engine over or when using the preheater (if fitted) or after the engine starts?

Have you checked the wiring at the back of the fuse panel, perhaps another cable has chaffed through its insulation allowing something else to draw power through the fuse?

As for the chart plotter throwing a wobbler on starting the engine, yes it is a common problem as the starter motor can pull the volts down to 8 or 9 volts and the plotter cuts out. Solution is to wire the plotter to the house batteries (leisure bank) and start the engine off the start battery - that way the leisure bank is not pulled down below the plotter cut off voltage.
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[Bosunof]

Thank you all for some useful help. Time to get the meter down to the boat and get it sorted.

Cheers