Topic: Main Fuse MADNESS..join the fun!

[chippyfive50]

Not long ago, in a land far far...well my garage, I did a "frame off" of my K4.
It has a new wiring harness,battery and DYNA S.
rode it 500+ miles, then started blowing main fuse. I inspected the fuse box, It was TOTALLY corroded on the back side.
I replaced it with a new one from auto pats store, and replaced / rewired and hand soldered the sub-harness from the fuse box to the main harness.
reassemble - fixed.
So i ride another 200+ carefree miles over a months time.
It happens AGAIN.
Every time i turn the key on, blown fuse.  SO...
I replace the key switch with my spare, no change.
I then try the lightbulb test, wiggle all wires, move all switches etc.
Next I disconnect every thing from the black power leg, light stays on.
Disconnect the black leg from the regulator, light goes DIM. 
So I connect my spare regulator, light is bright again.
WTF. 

With all connections from the black power leg disconnected, I put the fuse back in and it doesn't blow.
SO>>> one by one starting with the regulator, I reconnect every "hot" wire, and the fuse does not blow.
I now have the system back together, and it works flawlessly. I over wiggled every connection and bend, no failure.
I did a continuity test for short across all pins in the harness, no failures.
I removed the chain cover and wiggled and inspected the harnesses and connections and the look good, no short.
It is fixed until I get 100 milles from my house, but not solved..

any ideas or antidotes would be great.

[mystic_1]

You could have a temperature-induced short going on, something is shorting out when it's hot.  I'd pack along the meter and drive it until it fails, then diagnose it right there on the side of the road.

mystic_1

[Trevor from Warragul]

I had a similar problem on my 350/4.  I unwrapped the tape on the main harness and found a bucket load of corrosion surrounding a poorly fixed broken wire - damned previous owner!  (Oh wait, it was me who did that repair years before..)

I grafted in a whole lot of new wires and ended up replacing EVERY connector in the headlight (using dielectric grease).  I was amazed at how much brighter the idiot lights and indicators were, and the neutral light no longer pulses in time to the ignition.  Oh, and the fuse stopped blowing..

Trevor