Blowing the main 30 amp fuse

[DenyP]

In the last couple of weeks I have found the main fuse blown twice now on my XS1100E. I have replaces the fuse box with the spade box from TC.
I have done a cursorily inspection of the wiring loom and nothing stands out ie: bare spots etc. I know this is probity a intermittent short to ground some where. Any suggestions or advice in tracing down my problem?

Deny

[CatatonicBug]

Have you tried sniffing around the bike right after it blows the fuse? If you smell electrical smoke, that might narrow it down a bit.

[DenyP]

I haven't. It has been unreal. I will start the bike, back it out of the garage. The engine dies and no juce. I will try the sniffer to it when and if it happens again. In the two times it has happened, I just replaced the fuse and away I go. Should this fuse be a slow blow type?

Deny

[CatatonicBug]

Yes. These fuses take a little bit to blow. They are not instant. It has to heat up enough to melt the wire inside the fuse. You definitely have a short somewhere, but not sure where to look. Maybe the big white plastic connector behind the fuse block panel (wires to the alternator)?

[JeeP]

Might sound stupid at first, but have you tried to remove the gas tank and bench and start it in the dark. Usually when you have a short, it produces small sparks. Manipulate the electrical harness and see if you see small sparks.

[DenyP]

I will try that JeeP. The intermitant nature and timing of this problem is such that this may take some time to trace!

Thanks

Deny

[DiverRay]

Denny,
My now parked '79 had a short IN the wire harness! under the tank, between the coils and the fuse box. I had to peel off almost all the tape to find and fix it. I think almost 30 years has started to raise some issues with the wires themselves...

[randy]

Should this fuse be a slow blow type?

NO!

Slow-blow fuses are for special circuits that are expected to have quick spikes like audio and ac power supplies. You want the standard fast-blow fuses. The fuse's job is to protect the wiring. The LAST thing you want is a slow-blow fuse. Also be certain you have the correct rating of fuse. Can't count how many times I've found a higher than normal fuse in a circuit cause the ass PO figured the normal one keeps blowing but the higher one won't so leaves the higher one in.

[dbeardslee]

Deny - two places you might look - behind the fuse block mounting plate and inside the headlight bucket. There's a big white wire behind the mounting plate that's notorious for burning off it's insulation and shorting out the works. Inside the bucket is a three-prong connector for the ignition switch, which also seems to be a weak point. My $.02.

[skids]

Higher wattage head light? Other new draw on the system? Also, you might check to see if your volt regulator is allowing too many volts at higher throttle. Higher volts mean more amp draw total. Is your battery fluid boiling away?

[randy]

Higher volts mean more amp draw total

Um, no, higher volts means LESS amp draw total. BUT higher volts will blow out stuff

[XJOK2PLAY]

Ya might try this...

DenyP,

If all else fails ya and the problem still persists, disconnect the battery, then using either a DMM meter or analog set to continuity mode or one of those test lights that check continuity, ground one end to the frame, and the other to the wire in question and see if you get continuity. Then, use the "divide & conquer" method until you determine which section of the harness has the short. Checking unpowered circuits w/ continuity really can help speed up the process to pinpointing where the problem is. But, ya also have to remember... there are some things that can simulate a continuity. Flashers, elec. motors, transformers, alternator windings... even 1157 bulb filiments. The trick is trying to make sure you're only using this method to test JUST the wire in question. Hope this'll help ya find your problem.
Regards,
Bob

[skids]

Um, no, higher volts means LESS amp draw total. BUT higher volts will blow out stuff

Here is my line of thinking (probably wrong...)

V=IR or I=V/R

If R is a constant, as Volts increase, I increases in proportion.

In terms of power transmission through power lines, I understand that the current is lower at high voltage enabling smaller lines to the transformer.

I am waiting for a clubbing...

[randy]

You just contradicted yourself.

As the voltage increases, the circuit will draw less current. The total watts consumed will remain constant.

[gareth]

I spent a long time last week tracing a fault on an old 1961 Honda Dream 305. Some of the repairs on the harness went back to the Kennedy administration and the intermittant faults were a huge pain to track down.
I picked up a continuity tester at the local autoparts store that had a sharp pin that allowed me to stab-test a line without having to be at a terminal point. It was a big help especially for testing wires that were bunched together in a harness.


Ich bin ein Fault-on-a-liner.

G.