Signal Fuse keeps blowing - how do I find the problem?

[Guest]

My signal fuse keeps blowing out with in 3 mins, give or take, of riding. I've looked though the wiring diagram and checked every component that uses that fuse, and traced the wires with no luck. I have a multimeter and circuit tester, but I don't know how to use them to find the cause of this reoccurring problem. I've been looking through the forum and watching youtube videos trying to figure this out. So please can anyone tell me how to find the cause of this problem? Thanks in advance.

[Grimly]

Mysterious random blowing of that fuse can often be caused by the loom shorting to ground up at the steering head, as a result of decades of wear and tear.

[seanarthurmachado]

My signal fuse keeps blowing out with in 3 mins, give or take, of riding. I've looked though the wiring diagram and checked every component that uses that fuse, and traced the wires with no luck. I have a multimeter and circuit tester, but I don't know how to use them to find the cause of this reoccurring problem. I've been looking through the forum and watching youtube videos trying to figure this out. So please can anyone tell me how to find the cause of this problem? Thanks in advance.

It would be helpful if you described what model and year of motorcycle you have.

(Most of us place it in our signature).

when you say the "signal" fuse blows, are we speaking about the turn signal fuse ?

When does it happen ? does it occur when only using the signal ?

If the bike is sitting still does it still blow (wire hitting the frame when moving ?)

You would need to check the whole loom, every inch, including wires at the "ears" for the turn signals.

(My own bike was a mess of random wires bundled up in cheap old electrical tape in spots until fixed.)



sean

[posplayr]

You find it by disconnecting things until it does not blow.

Or the more sophisticated way is to measure the current in the signal circuit and see how much current you actually drop when you remove something and see if it makes sense.

It is probably not a light bulb.

I would suspect a short and do as Sean is suggesting do a physical inspection of the harness.

[MechMessiah]

It's an 82 gs650e. It was someone else's project bike and now it's my headache. And yes, it's the turn signal fuse. The circuit also includes the Horn, Gear Indicator, Neutral Light, Brake Light, and Turn Signal Relay. I've yet to pin down exactly when it occurs but it can happen when sitting still or moving, and it does not blown immediately with either powering the bike on, starting the engine, or using the turn signals. I have done a visual inspection of of the whole wiring harness and there are no obvious problems. I pulled the tank, opened the head light, checked the ears, and tail light housing. I was hoping there's something I can do with the multimeter or circuit tester to ferret out the problem.

[Grimly]

There's a simple non-destructive method;
in place of the fuse, wire in a test bulb, and wiggle the harness at various spots until the bulb lights up.
You've then found the short.

The other way - and I've seen this done for real, but don't actually ever recommend it.
Replace the fuse with a 6mm bolt and do the same as above.
The resulting charred mess will end at the short.
Well done, you've found the short.

[cowboyup3371]

The wire is shorting out some place either because a connector has gone bad some place or there's even a very small cut in the wire that touches the frame. Really look at all of the wiring inch by inch strand by strand from the front of the harness to the back. Look at each wire from the turn signals themselves to their connectors as well as their ground wires. Check the horn wiring as well.

You'll probably won't see it from a casual look of the wiring but even the smallest nick can create a problem if even one strand of wire is out of the sheathing and touching metal.

[MechMessiah]

There's a simple non-destructive method;
in place of the fuse, wire in a test bulb, and wiggle the harness at various spots until the bulb lights up.
You've then found the short.

That sounds very similar to a circuit tester. A gator clip on one end, sharp metal probe on the other with a light bulb in between. Correct me if I'm wrong, but can't I use that in the same way?

[Grimly]

That sounds very similar to a circuit tester. A gator clip on one end, sharp metal probe on the other with a light bulb in between. Correct me if I'm wrong, but can't I use that in the same way?

Yep; just reverse it and clip the lead to the fuse load terminal and the probe to the + battery terminal.

[Brendan W]

First place I would look is inside the left handlebar switch. Some of them have been repaired sloppily.
Second place would be under the coils. Some of the original ties to the frame were metal and they rust and open allowing the harness to drop towards the cam cover resulting in heat damage to plugs and wires.

[geol]

Some good advice already given... one thing I would keep in mind... on my 80 GS1000GL everything powered through the left handlebar switchgear is through the circuit that uses the orange/red wire from the fuse box. I think that would be the one blowing on your bike. Horn, headlight and turn signals. Since there is a good possibility that you have a hot wire touching ground just a tad, it might not hurt to disconnect the headlight (have to open headlight shell), turn signals and disconnect horn leads. Ride the bike and see if the fuse melts (might want to buy a few extra 10A fuses). Then plug in the headlight and see if that causes the fuse to blow after a bit. If not, plug in the horn leads and check then the turn signals. This may allow you to find the specific component that is causing the problem. Once you have isolated the actual component, look at a wiring diagram and chase the wires from the left switchgear to the component and see if you can spot some bare wire or perhaps a bad connector.

[robertbarr]

There's a simple non-destructive method;
in place of the fuse, wire in a test bulb, and wiggle the harness at various spots until the bulb lights up.
You've then found the short.

A similar approach would be to just pull the fuse (leave it out). Use a meter with a good continuity tester (buzz / beep report). Measure between the load side of the fuseholder and ground. Now jostle the harness here and there. When you hear the beep, you know you're closing in on the gremlin.

[MechMessiah]

Thanks for all the advise! I'm about to go out now and start working on it. Wish me luck.

[MechMessiah]

So does anyone know of a good machine shop around Baltimore? I got the short fixed, it was at the front brake switch. Once I had that done I figured I'd take care of the next issue I had, a bad valve cover gasket. Well I already had the gasket around because I tried to fix that on my 650GL but some bolts snapped and it's now my project bike. Well low and behold the same damn thing happened again, but more this time. Now it's 5 snapped bolts in the cylinder head.

...anyone around Baltimore wanna buy this damn thing?