12v Fuses

[Duccout]

I have a Mototrans Strada which has 12v electrics as standard. I have been cleaning up some of the wiring and have come across a problem with the fuses: one was missing completely ( that led to some head scratching) one has been replaced with a radio fuse, and the other two are both 15A. As I do not have a clue about electrics, can somebody who does help me by telling me what amperage fuses should be in the circuits?

Cheers,

Colin

[Geordie]

Colin, I looked up the owners and parts manuals at lamaneta and neither list the fuse amperage. The wiring diagram in the Owners shows a 4 gang fuse box.

Fuses are to protect wiring, not bulbs.
For instance, a 25W bulb at 12.5V draws 2A. In theory, a 2.5A fuse would suffice. Add up the Watts in a circuit and go up to the next available size should do it with some safety.

An auto electrician I am not so usual caveats apply.

Ian

[JimF]

Ian is spot-on about calculating amperage.

But sometimes the amperage rush is higher because not all electrical loads are not purely resistive. This is why you might recall references to fast-blow and slow-blow fuses.

When you calculate all the loads on a circuit and the total amperage, add 20% more to compensate for variations owing to surge currents.

Ian’s also right about the fuse protecting the wiring. If you can’t figure out all the loads on the circuit, figure out the wire gauge and you can find tables online that will tell you the maximum amperage the wire can carry. Deduct 20 or 25% and use something close to that as your fuse value.

Jim

[Jordan]

Good advices.

[Duccout]

Thanks for the suggestions, I shall investigate, although I must admit to bafflement at some aspects of electrics; it is all witchcraft to me!

[Duccout]

There is one fuse that does not make sense to me on the wiring diagram - I cannot see how power is connected to it, but my bike has an extra wire, not shown on the diagram, that brings power to the terminal. It is obviously a factory fitment, being sheathed exactly as the other terminals, so could someone have made a mistake in the drawing of the wiring diagram?


Colin

[JimF]

Follow the wire at the other side of the fuse’ that is to say where it goes so as to find the fuse’s purpose.

BTW, fuses are pretty much voltage indifferent meaning there is no such thing as a 6V fuse or a 12V fuse. You’ll see some fuses have a voltage rating but that has to do with a maximum voltage potential before the fuse may not be able to adequately interrupt the flow of current within a prescribed amount of time.

Fuses are also AC and DC indifferent.