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Author Topic: Diagnosing electrical problem  (Read 1123 times)

Rich Mintz

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Diagnosing electrical problem
« on: March 05, 2014, 03:33:29 PM »
Hi,

My 2010 bike (the Haunted C5 of Doom) has another issue. Today after 5 blocks of ordinary city riding, the main 20A fuse (#3) blew.

I replaced the fuse with a spare, started up the bike, and before I could get moving, it blew again.

I replaced it again, started up the bike again, and before I could get moving again, it blew again.

I opened the battery cover, and covered over the positive terminal with electrical tape. I also taped over the plug end of my (attached) battery terminal harness, which hangs loose on the side of the bike, with electrical tape.

Then I replaced the fuse again (with the regulator fuse #2, because I was out of spares) and turned the key to On. Before I even had a chance to start up the bike, the fuse blew.

Battery appears to be fully charged.

Some notes:

- Haven't ridden the bike in 4 days
- Over those 4 days, bike was on the battery tender. When I put it on the tender, it blinked "charging, at 80% or better"; this morning the tender was green (full charge).
- Before I put it on the tender, battery voltage was normal (12.81, I think)

What do I check first, and how? I can bring a multitester and basic tools to the bike.

All the spare fuses I used were factory (original) fuses.

Remember that I had a problem relatively recently where the engine faltered and then the main fuse blew while I was "pushing" the engine (high throttle uphill at high speed in high gear). This may be related.

Bike is parked (illegally but safely) on the street. If I have to, I can push it the half mile to my garage.

High On Octane

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Re: Diagnosing electrical problem
« Reply #1 on: March 05, 2014, 04:18:16 PM »
99% of the time when a fuse blows immediately, you can almost guarantee you have a wire grounding out on the chassis somewhere.  Start looking for a frayed/cut/broken wire.

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Rich Mintz

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Re: Diagnosing electrical problem
« Reply #2 on: March 05, 2014, 04:21:11 PM »
That's what I was afraid you would say. I have one of the slightly older C5s with a rat's nest behind the headlight and another one under the seat, so I'll probably have to push it to the garage and take the whole damn thing apart...

Ducati Scotty

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Re: Diagnosing electrical problem
« Reply #3 on: March 05, 2014, 05:55:53 PM »
99% of the time when a fuse blows immediately, you can almost guarantee you have a wire grounding out on the chassis somewhere.  Start looking for a frayed/cut/broken wire.

Scottie J

+1.  Some good places to look are where the wiring exits the triangle box, near the back of the tank where the wiring crosses the frame and headstay bracket, near the front of the tank where the loom crosses the steering tube.  Also, you can get circuit breakers that replace the fuses, they're maybe $10-15.  Get the kind with a reset button, not the auto reset kind.  I wouldn't leave it in there long term but it's just the thing to diagnose this problem without buying 100 fuses.

Scott


Ducati Scotty

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Re: Diagnosing electrical problem
« Reply #5 on: March 05, 2014, 06:48:52 PM »
Exactly!  A little more than I thought.  I think the self reset ones are less.

Scott

Rich Mintz

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Re: Diagnosing electrical problem
« Reply #6 on: March 05, 2014, 06:51:41 PM »
The self reset ones are much cheaper. But what's the point of a self-reset fuse -- isn't that just like bridging the fuse socket with a wire?

no bs

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Re: Diagnosing electrical problem
« Reply #7 on: March 05, 2014, 06:59:49 PM »
my blown fuse was caused by the taillight wires rubbing through on the fender where the grommet came out of the hole.
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Ducati Scotty

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Re: Diagnosing electrical problem
« Reply #8 on: March 05, 2014, 07:10:25 PM »
Good point.  Rich, is your headlight switch working?  If it is, turn off the lights and turn on the ignition.  If it doesn't blow, turn on the lights.  If it blows when you turn on the lights, well, you'll looking for a lighting short :)

And anywhere the wires pass over a metal edge or through a piece of metal is a good spot to check.

Scott

singhg5

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Re: Diagnosing electrical problem
« Reply #9 on: March 05, 2014, 07:33:53 PM »
I am sure you know all this since you had done quite a bit of work on wires sometime back. Wires may lose insulation by rubbing on metal at bends and can short anywhere throughout the bike, but most of the electrical shorts on RE have been reported amongst three or four areas - and most likely a visual inspection with a bright light will reveal itself.

Behind headlight nacelle
Under the tank rear behind the battery
Under the rear fender, wires coming off clips and rubbing against wheel
Around battery

Also notice if there is a connector sticking out a bit and touching metal.
« Last Edit: March 05, 2014, 07:41:26 PM by singhg5 »
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gashousegorilla

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Re: Diagnosing electrical problem
« Reply #10 on: March 05, 2014, 07:43:59 PM »
 May also consider replacing the main fuse with the stock 20A.. Then the other two with a LOWER rated fuse, like a five or a ten for now. In hopes that lower rated fuse will pop before the main. If it does.... you likely just isolated the circuit where the short is. 
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barenekd

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Re: Diagnosing electrical problem
« Reply #11 on: March 05, 2014, 09:19:58 PM »
A little late, but the first place you look, when you're troubleshooting, is the last place you did any work on the bike, even just touching stuff! the next place is checking Known problems sites as gleaned from the forum, or previous experience. My Goose stopped runnning on one cylinder this morning as I was coming home from a ride. Previous experience has told me the first place to look as at the plug connector, as the stock ones are a bit crappy. I ordered different connectors after the first problem, but I haven't put them in yet. Looks like a good opportunity to do it when I go out to fix it! If that's not the problem, then I'll worry about having to dig deeper.
Bare

« Last Edit: March 08, 2014, 10:00:47 PM by barenekd »
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Rich Mintz

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Re: Diagnosing electrical problem
« Reply #12 on: March 05, 2014, 11:06:48 PM »
Thanks all, and especially Bare for the common sense.  (First thing to do: reseat the plug cap and see if it helps.)

One question: I ordered a passel of 20A fuses which are coming tomorrow. Meanwhile, my local hardware store only had 25A, and I bought a few. Can I do some basic  testing with these? If it's successful (if the problem turns out to be trivial, like my spark plug cap is seated wrong), and the bike starts and runs, can I ride it home half a mile on a 25A fuse?

Ducati Scotty

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Re: Diagnosing electrical problem
« Reply #13 on: March 05, 2014, 11:11:01 PM »
Larger could melt wires, but you can probably diagnose and get home with some smaller ones. 

Scott

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Re: Diagnosing electrical problem
« Reply #14 on: March 05, 2014, 11:41:41 PM »
Rich:  You can check the spark plug cap but I guarantee it's not the problem.  The 12 volt circuits that the fuses protect don't go there.

As was said, use a systematic approach where you can.  Turn off the lights and try a new fuse.  If it blows it isn't likely to be a light system problem.
If turning on the lights blows, as was mentioned, the fuse the place where the wires go thru the grommet at the tail light is a good candidate.  So is the metal tab under the rear fender that keeps the wires from rubbing the tire as is the place where the rear lighting branch plugs into the main wiring harness.

Turn the handlebars back and forth leaving them in a different position than when you begin.  That will move the harness a bit.  Try another fuse.  If it doesn't blow, the problem is probably with the harness where it enters the rear of the headlight casquette or where it tucks under the fuel tank.  It also could be inside the casquette.
If the fuse blows it might still be in these places but the chances of it is less likely.

IMO, getting a circuit breaker might be nice for future problems but it doesn't have much to do with your immediate problem.  Speaking of that area, I saw recently where someone posted a picture of a bare fuse wire sticking out of the fuse holder.  That's something to look at if you have the clamshell fuse holders.

Usually, the fuse will blow before anything visable on the wires show but after blowing several fuses, you might look for wires that don't have a nice smooth factory insulation on them.  The overheating the problem wire can have might cause the insulation to wrinkle.  A sure sign of a overloaded wire.
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