Blowing fuses; then i may have really screwed up.

[Shovel Jockey]

Out for a ride today on my, to this point, trusty 78E. Blew the main 20A fuse for the first time since I've owned the bike, (4 years and 22K miles). Replaced it with the spare in the holder and it blew 5 seconds after startup. It just so happened to break down in an area where you DO NOT leave your bike unattended on the side of road if you ever want to see it again. Getting desperate I resorted to the old cigarette foil around the fuse trick to get it fired and get the hell out of there. It worked but by the time I got out of no mans land my fuse holder had overheated and melted a degree. I know I have to trace wires to find the problem and replace the fuse holder. My question is do you guys think I may have screwed anything else electrical up with my hillbilly fix?

 

[NONclow]

Either too much load (recent lighting or elect part upgrade: higher wattage bulbs, charging sys change producing less than 200 watts?), or a regulator prob. Test meter time! What're your readings with:

Key off.
Key on, kill sw off.
Key on, kill on, engine not running.
"","", engine idling.
"","", engine @3500r's

Possible battery issue? Age? Electrolyte level low (lead acid)?

Kick/E-start?
Stock harness/not?

The last thing I can think of right now would be a wire rubbing/cutting against metal, even a low wattage running light.....

 

[weaselbeak]

Something is sure pulling more juice than the fuse can handle. A fairly easy way to trouble shoot is to start unplugging various things.... headlight, tail light, etc. one at a time. If the problem disappears you're in the right ballpark at least.

 

[fredintoon]

Hi Shovel Jockey,
my best guess is that you've a wire that's gotten trapped, perhaps in some recent fix, had it's insulation compromised over time and has finally grounded out to the frame.
Sometimes it'll take weeks or months for the trapped wire to finally ground out, too.
And in the spirit of your signature line:-
If you can beat eggs and whip cream why can't you milk chocolate?

 

[5twins]

The worst offender on my bike when I went through it was the headlight shell. There's a bunch of wiring crammed in there and it rubs on stuff. Second worst was about half way back, around the battery box.

 

[Shovel Jockey]

update on the wiring problem. It's something with the brake wiring. The rear brake light does not come on when the foot brake is depressed; that happened when the fuse blew as best as I can tell. Checked the switch for actuation but don't know how to test otherwise. Wires seem fine. What's seems to be blowing the main fuse is often when you hit the front brake the taillight dims and if left applied the fuse blows. Something's shorted somewhere. I went from back to front and found nothing obvious. Checked the Clymers and that's when things got real screwy. Mine's an early 78 and there was a change in wiring after my bike was built, but after tracing those wires I found my wiring harness routing has some early AND late features unless Clymers got it wrong. I unplugged the green/yellow wire leading from the front brake switch and that at least stopped blowing the fuse; probably leads to the problem too. Does anyone have any input?

 

[XSLeo]

With the brake switches unplugged, use a jumper wire on the harness side. Does this blow the fuse? If not the problem is the switches.
Leo

 

[gggGary]

prime suspects; as previously mentioned, at the grommets in the headlight shell. then pinched wires under seat and where they pass through rear fender (twice). ot always obvious, rubbing, vibration causes the insulation to get thin at a sharp edge. WER just found a break in the brake wire inside the thick black plastic tube at a kink near the steering neck.

 

[Shovel Jockey]

Thanks for the input, still digging.

 

[650Skull]

Continuity testing is the best way to find that fault. You have diagnosed an area so work from there.

 

[weekendrider]

If it has a short it could still also have continuity?
If you don't have continuity from the yellow wire at the rear brake switch and the green/ yellow striped wire in the bucket the connection for the two is in the right leg of the Y behind the backbone. About 3-6 inchs past the Y. It may have a crimp or may be soldered but will be tied into the yellow and wrapped separate from the rest.

 

[650Skull]

If it has a short it could still also have continuity?

Agreed. But even a partial brake will show up on a reading. A good connection shows no resistance, partial breaks will show some resistance, Corroded terminals will show some resistance and sometimes they go on to show non.

A good connection should show full continuity instantly.