Blown fuse

Diablouph · Aug 18, 2013

I started blowing my single 20A fuse. After a few, I looked to the obvious culprits, then I pulled the tank and saw that my main ground attachment to the frame where four wires are connected had loosened and while the wires, which are solder tinned, were still in place, the ignition ground lead could be moved in place, but not pulled out.

Could a momentary short then reattachment, maybe because of the engine vibrating, cause a “surge” which would blow the fuse, and if so what causes the “surge”?

concours · Aug 18, 2013

I'd sooner think a short would, maybe keep looking? Intermittent electrical, celebrate good times!

Hobot · Aug 18, 2013

If shutting off the key blows fuses then yes your lose of earth would too. In otherwords keep looking for the actual short not breakage of conduction. First place I'd check in tail lens, next the brake then the horn circuits.

Diablouph · Aug 18, 2013

I thank you for your help. I will now descend into the bowels of Hades, to confront the Medusa with only a mirror and a millimeter.

aceaceca · Aug 18, 2013

A Zener diode stuck closed will also cause this. Closed being fully conducting to ground. Happened to me on the road once. Bypassed everything and powered the Boyer only to continue on.

MFB · Aug 19, 2013

I got this fuse block from a Suzuki car at a wreckers yard many years ago.
It's mounted in the right hand side cover. The bike is a 1970 model with central oil tank. My side covers are home made.
Now at least a fault in a light or something won't render the bike immobile, and it narrows down the search area.

I still have the main fuse at the battery for added safety but it's a higher amperage than the others.
Cheers
Martin

bluto · Aug 19, 2013

One good way to track down a short is to replace the main fuse with a small 12V bulb...so long as the short is there it will glow brightly but will dim or go out once the short is fixed (depending on what is switched on, etc.)..saves on fuses while troubleshooting. Do not try to start and run the bike with the bulb in place though, it causes a substantial voltage drop that the ignition system would not like.

DogT · Aug 19, 2013

+1, and if you know how to use a voltmeter, it will help immensely tracking down the issue.

texasSlick · Aug 19, 2013

Divide and conquer! That is my remedy to find a short.

By divide, endeavor to separate your circuits by removing some leads to the main circuit. When fuses quit blowing, divide the previously removed ones some more, and keep trying. +1 to bluto and dogT.

batrider · Aug 19, 2013

Holy cow - Multimeters are so ridiculously cheap these days. Was at Harbor Freight over the weekend and they were $5. We do some work with high voltage at my job and we buy these things for use in production because if they get blown up we don't care. Perfect for troubleshooting old bikes though.

Blown fuse

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