Mirage1200TS electrical mystery

L

lawrence

Hero member
Location
Idaho, USA
My Mirage ran flawlessly on my recent pilgrimage to Wolfgang's rally.  After I returned home I washed the bike and the result was misfiring on cylinders 1 & 3. Since this happened after the wash, I thought it would be a question of a faulty connector to the RS coil.  I cleaned all the connectors I could easily access and the bike now starts and run strong.  However, I found a melted fuse that's a puzzle.  It appears to have melted from engine heat rather than the wire itself overheating, as the fuse looks to be intact.  I couldn't pull it apart due to the melting, so I don't know what I should replace it with.  15A ?  I took the photo below before I attempt any surgery on the wiring harness.  Any insights from the Laverda experts?
The attached photo shows the problem, taken from the RS of the m/c.
 

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Lawrence,

Don't think the engine would get hot enough to melt the fuse holder where it is... if it does, you've got other problems!!

With an ammeter, check how much the fuse has to cope with and fit the next larger one available.

To me it looks like a borderline fuse fitting, too much to cope with but not enough to blow. :o

piit
 
I don't use anything except a gentle spray from a garden hose for washing.

"With an ammeter, check how much the fuse has to cope with and fit the next larger one available."
Piet,
Being an electrical dunce, this recommendation is Greek to me.  Can I use a multimeter to measure the fuse's capacity?
I wonder if it's wise to fit a larger capacity fuse if this one is OEM.  (I've no idea if it is.) If the melting was caused by current, how would a larger fuse help?  I've not opened the case yet, but the fuse seems intact.
When I replace it, I'll fit a blade-type fuse there. They generally seem more robust.
Thank you for your suggestions.
 
Looks VERY non-standard fitment to me.
Why does it not live in the fuse box with the rest?
 
This should start with 'I'm not an electrician but'.
Hopefully your current surge was due to dampness and thus temporary.
I have done some electrical training recently, it was drummed into me that fuses are there to protect the wiring and prevent fires. Too much current and the wire core will heat up very quickly, so you need some caution.
 
When you say the fuse melted has the fuse actually blown? (check for electrical continuity between both ends, or check that there is 12v on the both sides when powered up).

If the fuse is intact but the case/holder/wire is melted I would assume this was down to an unrelated incident which blew a fuse previously (if the fuse rating was very excessive for the circuit it is possible that everything else would melt and the fuse would stay intact but this seems very unlikely).

If it is blown (and assuming it is on the coil supply line) there is either a short in the loom between fuse and coil or the coil itself is failing.

Either way increasing the fuse rating is not a good option unless you are sure that the existing fuse rating is too low.
 
Hi
It could be due to a high resistance contact either end of the fuse,possibly due to dirty contact faces or poor crimping of the wires in the fuse holder.This would not necessarily blow the fuse even if of the correct rating.
Neale
 
nealebms said:
Hi
It could be due to a high resistance contact either end of the fuse,possibly due to dirty contact faces or poor crimping of the wires in the fuse holder.This would not necessarily blow the fuse even if of the correct rating.
Neale
Click to expand...

Exactly what I was thinking.

It's unlikely to be an under-rated fuse because it should blow before getting hot enough to melt the fuse holder.

To answer your question Lawrence: You can't measure the capacity of a fuse with an ammeter. Well, not directly anyway. I think Piet was suggesting that you measure the current flowing through it to see whether it's pushng the limits of the fuse's rating.

Looks like you'll need a new fuse holder anyway, so get a waterproof type that won't be bothered next time you wash the bike. Any car or boat shop will have them. There's also heaps of them on eBay and they cost peanuts.

Cheers,
Cam
 
I am a bit obsessive with washing,comes from getting dirtbike really muddy.I don't use a pressure washer,just a strong hose.I use a product called CT18 truck wash,mix it up in a spray bottle.Hit the bike with it and hose off,wipe with a shammy.The point of this and whats really important is I always start the bike directly after and let it get completely warm.That cooks off any water sitting in the nooks and cranny's,never had a problem after doing this.
 
drying - use a leaf blower (or a broad blast with compressed air gun) - much better than running a cold bike up to warm IMHO
 
Here's an update on the fuse mystery.  The fuse never blew, but the surrounding holder was transformed into something of a Dali work. A hole had opened on the end that allowed water and whatever else the environment provided to intrude.  As the photo shows, the fuse was the wire-in-a-glass-tube variety; a 25A.  (Incidentally, this was in a line that runs from the + battery terminal to the 6-connector plug found by the frame tube to the right of the battery. I don't know if the original wiring provided for this fuse, Grant.) I have replaced it with a blade-type fuse which, as noted above, is well sealed and a better design in my view.  The bike starts and all seems well now. 
I'd be lying if I claimed to be completely confident, however.  This all began when cylinders 1 & 3 began to misfire after the bike was washed.  Water could have played a role in the problem, but I'm left with the question of why it never misbehaved when I rode through the rain on the return from Nakusp, B.C. Can it all be chalked up to not starting and warming it up after the wash?  Or, did I just have a guardian angel on board that kept me from being stranded on the roadside during that ride?  I want to believe the latter!
I just hate electrical problems!
 
A bad connection at a fuse could account for poor ignition performance and difficulty starting. That happened to my Ducati a while back. After poking around for ages with a multimeter and doing a lot of head scratching, I eventually found that the electrical system was losing about 3V through the fuse! Pulled the fuse out, cleaned the contacts and put it back in again and everything was sweet.
 
Dellortoman said:
A bad connection at a fuse could account for poor ignition performance and difficulty starting. That happened to my Ducati a while back. After poking around for ages with a multimeter and doing a lot of head scratching, I eventually found that the electrical system was losing about 3V through the fuse! Pulled the fuse out, cleaned the contacts and put it back in again and everything was sweet.
Click to expand...

HA ha, we did that 2 Barry Sheenes ago, PC rode the Seth african down limped in just after dark with no headlight, pulled the whole thing apart, fairing wise, which aint much  fun on a rgs, checkin wire and connections etc, fuckn dirty fuse, but we had Coronas and good times
 
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