Wiring short

M

Merkid

Well-known member
So now the lights on my GS1250FA went out on me a few miles from home. The engine started and ran well with only the front headlight operating so i was able to ride home using hand signals for turning and stopping. Thankfully no cops around and traffic was light.

It turns out the fuse for the 'signals' blew. This is usually a sign that one of the power wires to them has grounded somewhere. The wiring loom is wrapped all around the frame and taped up tight so trying to locate the ground problem looks like a pain.

Any suggestions on how to start sorting this out ?
 
Merkid said:
So now the lights on my GS1250FA went out on me a few miles from home. The engine started and ran well with only the front headlight operating so i was able to ride home using hand signals for turning and stopping. Thankfully no cops around and traffic was light.

It turns out the fuse for the 'signals' blew. This is usually a sign that one of the power wires to them has grounded somewhere. The wiring loom is wrapped all around the frame and taped up tight so trying to locate the ground problem looks like a pain.

Any suggestions on how to start sorting this out ?
Click to expand...
If you get lucky and it is still shorted (could confirm/try to track down with multimeter), an ir camera might save you a bunch of time as the short should be easy to see as well as the wire up to the short will heat up and be cold after. If it's an intermittent short your life is harder. For that you need to poke/prod/jiggle all along the harness until you get it to pop.

There are temporary circuit breakers that you can put in in place of a fuse to keep circuit protection while not using a case of fuses as you track down the problem. They arent really cheap, so it may be cheaper to use fuses. If it was an older bike without brains, I would wire in a lightbulb in series with the fuse to lower the power through the circuit without blowing the fuse everytime the short connected but on newer bikes with computers, I am leery of doing this without seeing the circuit diagram as I dont want to hurt the brain box.
 
Did it blow or just break from vibration ? The easiest thing to check is amperage at the fuse box.
Measure across the terminals of the offending fuse and see what you get. If it exceeds the fuse rating then its time to start digging.
 
Check the wires where they go through the stems on the signals, right close to the rubber mounts. The rubber lets the signals move from vibration but that movement can sometimes cause a wear problem with the wire insulation.
Incandescent bulbs? also check the bulb itself to make sure the filament has not broken and shorting internally.

... sure you don't have a mouse nest anywhere?

(y) wiring diagram, all electrical trouble-shooting starts there.
 
Doesn’t that bike use the 7 pin relay under the battery. Great spot to collect moisture. That’s the location on the sv650. Just did led bulbs and relay.
 
Don't exclude the possibility of an internally shorted bulb.

Check the wiring diagram and identify everything, and I mean EVERYthing, that is connected to that circuit. Chances are, this will be: Taillight (including brake lamp), license plate lamp, turn signal circuit, instrument lighting, horn, possibly running lights if so equipped. There may be others.

Now, go around the bike and unplug everything that can be unplugged in that circuit, except the instrument cluster (whose wiring is generally together with a bunch of other circuits that you need). Turn signals will have a connector nearby. Taillight will have a connector nearby. License plate lamp will have a connector nearby. Horn should have a couple of spade connectors right on it.

Switch everything off that is involved with that circuit and which has a switch ... turn signals, horn, brake lamp.

Now, the idea with the next step is to re-activate one circuit at a time, progressively checking its function, until you identify the moment the fuse blows. Option 1 is to do this with a number of spare fuses on hand. Option 2 is to do it with a multimeter set on measuring current (amps) on a scale that will allow reading up to 10 amps (normal capacity of that circuit). Either way ...

With everything unplugged, disconnected, and switched off in that circuit, turn on the key and verify whether the fuse remains intact / current reading remains low. The instrument lighting which is the only thing you didn't disconnect, should come on and stay on with the key as normal. If the fuse blows immediately, your problem is either in the instrument lighting or in the main harness up to the first (unplugged/switched-off) switching point in the circuit - that should narrow it down quite a bit.

Although nothing is plugged in at this point ... Activate the turn signals, first left, then right, then cancel them, then press the horn button, then squeeze the front brake lever, then squeeze the rear brake lever. The purpose here is to test the portions of the harness downstream of those respective switches. If the fuse blows when you activate a given switch, you now know that the fault lies in either the switch itself or in the portion of the harness between the switch and its respective load (connector).

If it survived that, plug in the taillamp connector. If the fuse blows, that's where your problem is. If it remains intact (instrument lighting remains on and your now-plugged-in taillamp works), squeeze the front brake lever, squeeze the rear brake lever. If the fuse blows when you activate any given switch, the problem is with the load operated by that switch (i.e. the taillight bulb or its socket or the pigtail-harness leading to it).

Then plug in the license plate lamp. There's no switch, so it should work. If it blows the fuse, there's your problem.

Then plug in one of the turn signals, and activate the turn signal in that direction. Yes, the flashing rate will be abnormal (or it may not flash at all) but our only concern at the moment is that the bulb works as opposed to blowing the fuse. If it blows the fuse, there's your problem. Same for the next one, and the next, and the last. Then plug in the horn, and check that function.

If it survived this process without blowing the fuse, then there may be an intermittent short, and these can be frustrating to diagnose. Throughout the above process, be on the lookout for insulation that is damaged, cut, or worn through. Pay particular attention to any place where a wire or harness is clamped to, or runs next to, any metal object.
 
Thanks guys, lots of good advice.

I spent the afternoon on my knees sourcing the cause of the blown fuse. After unplugging, re-plugging and testing with an ammeter all the feeds to this fuse, ie" signals, tach, horn etc, the problem turned out to be the wiring harness itself under the tank that as the problem. Things are very tight under the tank and it looks like the harness was rubbing for some time against the frame such that the protective sheath was exposed bare down to one small wire . So I shrink wrapped the wire and added additional wrapping to the harness just for added protection. Hoping that was the cure.

What is interesting is the bike is eight years old with only 13K on the clock, and i have had quite a few FI issues with it to-date. My early '80s GS1100's went up to 90K with only battery and tire changes.... oh well.
 
"quite a few FI issues with it to-date" Curious what the nature of your previous Fi problems were?
 
To 'Trials' question, the FI issues pertain to the bike being on it's 3rd fuel pump. The first one (Mitsubishi) acted up at 11K such that i could not get the engine over 4K rpm, the 2nd pump was a Chinese knock off that lasted for about 1K then lost it's pressure output. When I took it out, it would rattle when i shook it..... (n) The third one was a higher pressure version, US built and still performing well today.

To 'GVH's question, yes i bought it in 2015 . It had 5500 kms at the time.
 
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