so I have a 78 CX500... old but its a good first machine to get used to riding on. It has 2 fuse circuits, one runs the headlight, one runs the tail light and guage illumination. The tail light and guage illumination one popped on me a while back when we were moving it and I replaced it thinking it must have just gotten roughed up whilst beign put in a pickup, and it was fine for a month or so. Then about a week ago it popped again, which I believe was because i laid the bike down in heavy rain... didn't wreck, just trying to make an awkward manuever and lost traction in some mud and dropped it softly in the grass. Next time i went to ride it, that fuse was popped again, and when I replaced it it immediately poppd once more. I was gonna just get a slightly heavier fuse and see if the problem was small enough that that'd cut it, but w/e it is in the clusterfuck of wires is making a hell of a connection where it's not supposed to. It pops the 12V 10A fuses its meant to use so fast that the tail light can't even flicker on. I tried bridging that fuse socket with a pop tab, and the headlight dims to about 35% its normal brightness, and its not even cold out, so it must have the battery drawn to pretty much full tilt.

can anyone recommend how I should locate the bad spot in the wiring? I dunno if I'll ever find it just going through by hand. My friend has a multimeter, so we're gonna try that, which I guess means just starting by testing the whole circuit, and narrowing down the area being tested each time until we find the faulty wire. Is that how you would do it? I thought maybe if I could find some heat imagery goggles, I could go out at night and bridge the gap and then look for hot spots that show up on the bike. Would that work? Would a short bad enough to dim the headlight like that be enough to give a head signiature? Do any places rent heat imagery goggles? Is there some other similar way I could do this?


thanks for any help
-Jon

Thermal imaging isn't going to work since not much energy is disappated over time, unless you leave it on for a long time, which is a fire hazard.

I suppose you could disconnect everything on that circuit, plug it up and see if it shorts again. If it does, you have a short in a power wire somewhere. If not, its a device short.

ok so i havn't had time to actually undo all the wiring and redo it, but I did pull the tail lights outa the rear lens. The bulbs each have 2 separate filament circuits... one that stays on all the time as the tail light, and the other which illuminates in addition to the tail when the brakes are applied. The brake filament on both are in fine condition, but the tail filaments (which is the circuit causing problems) are in bad shape. one of them had actually melted enough that it broke away from its hanger wire and fell against the brake light wire and resolidified. the other is still in proper contact, but it looks like its done its share of melting and shrivelling too. I popped both both bulbs out, and it still short circuits somewhere.

Any speculation of what to try next? I've seen like household lightbulbs where the filament structure collapses and the hanger wires bridge to eachother and that kicks the circuit breaker, but that doesn't seem to be the case here, otherwise it wouldn't keep shorting when I took the bulbs out. Would it?

thanks
-Jon

Current is not flowing through them when you hold one in your hand and turn it on, is it? :p

Are the light bulbs the only thing that's on that circuit?