Possible short?

[bikey2003]

I have a 1980 Midnight Special, that blows the 20A "signal" fuse when I start to rev up the engine. I disconnected everything
on that circuit, and all the gages, and the problem still occurs.
Just before the fuse blows, the engine will hesitate, the fuse blows, and the engine runs fine again. Any suggestions/solutions will be much appreciated, otherwise I will probably have to unwrap the whole electrical harness. Thanks..Terry

[TopCatGr58]

Hey Bikey,

Blowing a fuse indicates that you have a direct to ground connection happening somewhere. The engine revving causing it could be JUST vibration that shakes the frame, and causes the offending wire to make contact, shorting out.

The TCI is under the seat, and there are turn signal wires that run around there as well, although going to the lights they shouldn't be energized UNTIL you are using the signals. There are also both flasher units in that same area, the regular signal flasher, and the 4 way emergency flasher on the left side above the battery.

You could unplug both flashers, and then with it running, plug in one, and rev and see if blows, then the other, could help you isolate which flasher circuit is involved?!

Also, check your charging current, are you getting more than 14.5 volts at the battery when you rev the engine??
Happy Hunting!
T.C.

[bikey2003]

Hi, Thanks TC, but I even ran the bike with everything disconnected including both flashers the tach and speedo, headlight, and anything that wasn't needed for the engine to run.
I will take your advice and see what kind of voltage I get at the battery, but I will bet that it will drop at the instant the "short" reappears, since the tach will "freeze" and the neutral light will dim at the same instant, before the fuse dies...Terry

[motoman]

You might check the wiring harness where it runs on left side of top frame under fuel tank.........may be a suspect place.........don't ask how I know this. Avoid un-raveling harness if at all possible. You'll open a can of worms you may regret. I'm sure you'll find the source of problem to turn out to be a simple fix.

[bikey2003]

Thanks motoman, that was going to be my next strategy. I did unwrap two harnesses from the forks forward, and some of the wiring had moisture there, but no bare insulation. It should be easy to re-wrap.

[LoserShoes]

If it has an emergency flasher switch on the bottom of the turn signal assembly, I think I remeber that there is a hot wire to that switch, and the terminals will corrode and break loose. Take the turn signal switch/hazard switch apart and look there.

Steve

[bikey2003]

Thanks Steve, but I had already disconnected that whole switch assembly loom from the main harness, and the short was still present.
I will proceed to unravel the main
harness , starting at the fuse box and work my way up, this weekend.

[randy]

I would bet that the rectifier/regulator is faulty. Try unplugging both plugs and run it and see what happens.

[bikey2003]

Randy, I did that too! same problem...Terry

[bikey2003]

Fixed!!!

Its Fixed! Finally-after unravelling the entire harness covering, I found the offending culprit-the power wire to the fron brake switch was chafing against the tachometer pulse/feed wireand was shorting through that circuit-I removed bad wire, spliced in a new one, and it's good to go! Thanks to all for their help with this, too, and keep the rubber side down!