blowing a fuse

[Nibor]

hey guys,

Problem: i keep tripping a fuse, the 7.5 amp for the turn signals, tail light, and pilot light (this is most of the dash lights?). this happens intermittently, so sometime during a ride it trips. i've pulled over, replaced it, and it trips as soon as i turn the bike on. not sure if i've had the indicators on at the time i turned on again. i've also replaced it and it hasn't tripped straight away, but lasted a while until it blew mid ride again.

we replaced the tail light as it had blown, and this seemed to fix the problem, but it tripped again today, whilst i was riding.

background: i'm riding a 1998 M750. i binned it a couple of months back, all of the indicators got damaged but we glued them up (the casing, electrical was fine with them all). other than that i haven't done anything with the bike mods wise, not that would affect electrical.

not sure exactly what to do, any ideas?

[Nibor]

just replaced the fuse after it had blown on the way home today. everything now works fine. 
problem is, i haven't isolated the problem, it's just intermittent. tried every electrical combo i could think of, starting with indicators, brakes, high beam, all that. nothing blew it.

has blown in the middle of the day on a dry day, riding, so guessing it's not water related. maybe an exposed wire somewhere, worn through or something?

[Ddan]

You don't say what you've got for a bike, but the tail wiring on older Monsters could get pinched under the seat

[WetDuc]

It definitely sounds like a short.  Got a multimeter?  Check the wire runs to see if you have a bad one.

[Howley]

Mate I've had the same problem on my '94 900 for ages. I never isolated the problem, but I stripped the sheath off the tail light harness and checked it, then re-wrapped it, and it hasn't blown since. I wouldn't call it 'fixed' but yeah, it hasn't done it since.

[Nibor]

It definitely sounds like a short.  Got a multimeter?  Check the wire runs to see if you have a bad one.

i think it's a short, but i've no idea where, and the other problem is it's not always shorting. for instance it blew on the way home from work today, got home, chucked a new fuse in and it was fine. if it was constantly shorting, that new fuse would have blown straight away. then i could have used the multi, and tried to trace it.

Dan - i did it's a 1998 m750. the wiring running to the tail via the underseat looks fine, i just had a look. fair bit of excess, but the cable ties make sure it is out of the way.

[Howie]

You have a short somewhere, probably a short to ground.  Problem with intermittent problems is all tests well asl ong as all works well.  You need to duplicate the problem.  Go to the auto parts store, get a 7.5 amp circuit breaker, some wire and some connectors and set it up so you can use that as a fuse so you don't keep blowing fuses.  Now start wiggling wires until the breaker blows.  When you narrow it down to that area you will be on your way to finding the problem.  Dan's suggestion to look under the seat is statistically valid, but start wiggling and moving stuff.  Also wiggle the wire harnesses running down the head tube. 

[scott_araujo]

Since this is turn signal related, check wires near the head tube.  Might be a wire with worn insulation shorting when you turn the bars.  Those are really the only wires that move on the bike.

Scott