Modern Vespa

Hi,

Fuse blew out twice. I think it's from a really worn out wire connecting from the junction box. Exposed wire almost disintegrating; used electrical tape for the moment.

1) Any good tips on troubleshooting root cause of a blown fuse? Going to replace that wire mentioned above, but just in case that isn't it.

2) Should I go with the glass fuse instead of the plastic fuse (see attachment)? Benefits of one over the other, besides seeing the glass fuse being available more than the other. I'm assuming I need to replace the fuse holders as well, right?

If the fuse is blowing due to an intermittent short, that's one of the more difficult problems to trouble shoot. All you can really do is inspect every inch of the circuitry protected by the fuse for obvious shorts.

As far as one style fuse versus another, all fuses are electrically the same. Well, almost. Some fuses are designed to allow very brief transient surges to pass without blowing the fuse, and are called "slow-blow" fuses, but these are not commonly found in automotive applications.

For circuit protection on your Vespa, any automotive type fuse of the proper amperage will work.

Al

Those plastic or ceramic VW-type fuses can be annoying - their tips can corrode easily and they can come apart when removed from "pincher" type fuse holders, but in a dry area they work just fine. I wouldn't bother changing it.

As for finding the problem - Al said it, just check every millimeter of every part of the system and you'll find it. Or put in a 30A fuse and see what melts.

- Eric

Yeah... somewhere you've got a power short to ground. On the Super i was just doing the electrics on, someone had attached the glovebox and pinched a wire coming off the fusebox... so it was shorting all power off the battery to ground and was passing enough current to start melting the insulation on the wire....it was smoking off!

That was a pretty obvious find... just look for the smoke and follow the wire to where it's grounding to the frame!

Tried the following:

1) Changed the red wire coming from the junction box. Fuse blown again when bike is running (on it's stand). Last of the 8 amp fuses.

2) Taped up a couple of exposed wires in the glove box cowl: a) positive wire to the fuse clamp b) the wires going to the flasher unit. Only had a 5 amp and 16 amp fuses left. Used the 5 amp and it worked. Thanks HP.

I guess it's pretty sensitive in there.

Luckily, I didn't have to go into the headset.

Thanks everyone.

Cheers,
Tam