Main Fuse blows at speed!!!!!

frankblack · Post by **frankblack** » Mon Mar 07, 2005 11:01 pm

Doing around 75 mph down the highway Saturday afternoon and the bike just shut down -- lost all power -- DEAD!

No lights -- nothing

Was able to wangle my way to the emergency lane -- pulled the seat -- and saw that the 15Amp main fuse had not "blown" (as in separated metal) but had actually melted -- looked like an old-fashioned flash bulb!

Any ideas as to what might have caused this? Time to start looking for a new voltage regulator?

I'm a bit bewildered.

And, oh yeah, I had a spare and was off and running in no time.

Ideas? Similar experiences?

fasterdammit · Post by **fasterdammit** » Tue Mar 08, 2005 3:27 am

I can't recall if it was the main fuse that went, but had a similar experience in terms of losing all power in a flash - wasn't doing 75mph, but just a weird coincidence of cornering, downshift/throttle blip, cancelling a turn signal and accidentally hitting the hibeam or convergence of the sun and moon or something equal bizarre. Turned out to be a blown fuse, and quickly replaced. Now I carry a full contingent of spares under the saddle.

Post by **Skins** » Tue Mar 08, 2005 7:22 am

Look for a wire or connector that's been shorting against the frame or against another wire or connector. If you look carefully you might be able to see signs of burning or melting. Best of luck!

frankblack · Post by **frankblack** » Tue Mar 08, 2005 11:15 pm

I did notice a loose ground that looked like it was connected to the blinker relay. Could this possibly be related to the blowing of the main fuse? :screwy:

Going over the bike with a fine tooth comb 'til I figure this one out.

Thanks for the input.

F

Post by **Skins** » Wed Mar 09, 2005 12:40 am

Now I'm not too good on electrics, but I think a loose ground wire won't cause a fuse to blow, it'll just stop whatever it was supposed to ground from working.

A fuse will blow when a curcuit it is controlling starts passing too much current, which can be caused by a short between two circuits (making one big circuit which then draws too much current) or a short between a circuit and the frame. Also components like relays can develop an internal short, making two circuits run together and draw too much current. At least that's what my limited understading of electrics tells me.

It could take a while to find the problem. Try connecting a test light across the fuse (take the fuse out and insert the leads from the test light) then turn the ignition on. Then turn other things on (lights, horn, indicators, operate the brakes, etc) also jiggle wires, connectors and components and see if the test light goes off or flickers. If it does, the problem may be related to what you turned on or the part you're jiggling. Then look there for the short.

If the test light goes out when you start and rev the motor, the problem might be in the charging circuit, which I really do know nothing about, I'm afraid. But I think the problem is likely to be somewhere else.

Keep going, and you'll get there!

frankblack · Post by **frankblack** » Wed Mar 09, 2005 12:44 am

Thanks, skins.

I've had this bike since '97 with no problems (an '88 Paso LTD) -- and I'm trying to keep it that way.

It may be a while, but I'll post when I figure it out.

In the meantime, I think I'll ride my Guzzi V11 exclusively...

F

Post by **Skins** » Wed Mar 09, 2005 1:05 am

OK! I'm sure the Guzzi will repay you for the exclusive attention!

Post by **jcslocum** » Wed Mar 09, 2005 10:43 pm

The melted versus blown (popped) information is significant. It means that the wiring and fuse ran at an elevated current draw to make it get hot enough to melt but not blow out. This is usually caused by dirty connections but with the Paso and it's crappy electrical system, who knows.

Clean and inspect everything before it burns up. To see what happens when they burn, look at the pictures of Jules bike in Japan...

Good luck and let me know if I can help in any way.

frankblack · Post by **frankblack** » Wed Mar 09, 2005 11:05 pm

jcslocum wrote:The melted versus blown (popped) information is significant. It means that the wiring and fuse ran at an elevated current draw to make it get hot enough to melt but not blow out. This is usually caused by dirty connections but with the Paso and it's crappy electrical system, who knows.

Clean and inspect everything before it burns up. To see what happens when they burn, look at the pictures of Jules bike in Japan...

Good luck and let me know if I can help in any way.

JC --

Thanks for the info. I'm barely sufficient at bike electrics, so -- where should I begin and end this trek thru "everything?"

Again, thanks in advance.

FB

Post by **Skins** » Wed Mar 09, 2005 11:15 pm

aha ... that makes sense. Thanks for your valuable information, Jon.

Post by **jcslocum** » Thu Mar 10, 2005 12:19 am

Thanks for the info. I'm barely sufficient at bike electrics, so -- where should I begin and end this trek thru "everything?"

Again, thanks in advance.

FB

Start with the battery and it's cables. Then follow the neg cable to the engine. Remobve the bolt and clean with scotch brite both the engine case and cable end. Tighten bolt.

Next look to the things that are "on" while you are riding, like the headlight. Have you put in a higher wattage bulb? Do you have any other electric accessories?

Remove and clean the ignition switch. ALL electric (excpept starter) goes thru the switch. It's a stupid arrangement but that's how they did it.

Next follow the wiring harness from the fuse panel toward the Ign switch, undo all of the plugs, inspect for corosion and clean as needed.

Pull the individual fuses, inspect and clean. Inspect and clean connections to the voltage regulator.

Overall you are looking for things or conditions that will cause resistance. Resistance = heat. Clean, clean, clean. Did I mention to clean everything?

This is a pic of Jules bike: http://tinyurl.com/6aodm

Modify the wiring to include relays to switch the electrics. See the starting thread down the page.

Post by **Skins** » Thu Mar 10, 2005 1:08 am

OK. So you're not looking for a short so much as a bad (dirty) connection, Frank.

Jon, can a loose (intermittent) connection cause a circuit to get hot?

Post by **jcslocum** » Thu Mar 10, 2005 11:29 am

Skins wrote:Jon, can a loose (intermittent) connection cause a circuit to get hot?

Sure can.

redpaso · Post by **redpaso** » Fri Mar 11, 2005 5:50 am

FYI I just replaced my Voltage Regulator/rectifier as it was faulty (I would not replace it othervise). What happened with me was that it would start & while warming up if it cut out would not re start. I replaced the battery & it was fine for a month & then while out for a ride I had done 120ks & as I eased off the throttle into a 90 degree bend it started to backkfire & splutter. I tried (once bend negotiated) to apply power & it continued to backfire. Once I eased the throttle again she cut out. Still had lights etc but there was no way she would fire up. the battery was completely drained (not good for a new battery). I replaced it with a Japanese one as recommended by the Ducati dealer (North Coast V-Twins) as teh original is expensive & has a poor reputation. I could have had it reconditioned but though tthat replace was a wiser decision. The Japanese one is more powerful & reliable & a third of the cost. It did require some rewiring though but is is back on the road & better than ever.

Don't think this is your problem but you can never have too much information.