Fuse Blows When Shutting Engine Off - Sometimes

[Drastik]

It doesn't happen every time, but sometimes the 20A fuse blows immediately after I shut off the engine.  Note:  The bike is not stalling.  It does not blow while running.  It only blows after I intentionally shut off the engine using the switch. 

I took the bike (new to me, and my first bike) to a parking lot with a friend yesterday to do some practicing before I take my basic riders course in a couple of weeks.  We were there for a couple of hours. No problems with the fuse.  Later that night, the new battery was fully charged, so I installed it and ran the bike in neutral, on the side stand for a couple of minutes.  As soon as I shut it off, the fuse blew.  Installed a new fuse, started the bike again.  After I shut it off this time, the fuse did not blow.  This was randomly occurring before the battery swap too. 

I'm in the process of checking the harness for shorts, but wanted to post this up in case others have some experience/advice on this scenario.  Bike is a 93 GS500.

[adidasguy]

It most likely is a short happening in your right hand control. You might want to replace it.
The headlight and starter wires are in that control. The jarring of the stop switch is possibly causing one of the wires to short to the frame inside the control.

[Drastik]

Thanks for the helpful reply!   

I'll take a good look at this area (best I can, at least).  If I don't find any evidence of wiring issues elsewhere on the bike or find any other symptoms - I'll replace the right hand control as suggested. 

[gsJack]

The kill switch, starter button, and brake light switch are in the right hand control.  The turn signal, horn button and high beam dimmer are on the left.  Other than the dimmer the head and other lights are turned on and off by the ignition switch.  OP mentions turning engine off using the switch but is that the kill switch or ignition switch?

Anyway, I kill my engine by putting the stand down in 1st gear followed by turning off the ignition switch.  Why not kill your engine for a while with the kickstand and then pause to see if it affects the fuse and then turn off the ignition switch to see if that blows it and don't be too quick to replace the right hand switchgear unless you have an extra one laying around.

[Drastik]

I was referring to the kill switch, not the ignition switch.  BUT - I've been trying to recall the circumstances when the fuse has blown, and I'm thinking that it may be when the kill switch is used while the bike is on the side stand in neutral.  There are also times when I use the ignition switch, but since it's a random problem, I wasn't keeping track of these things. 

I'll start messing around with the different options like you mentioned and see if I can narrow it down some.  Thanks for the advice!

[Drastik]

Update - Well, after messing with it some more, the fuse blows almost every time ( 4 out of 6 times) I use the kill switch.  Using the ignition switch does not blow the fuse.  There were a couple of times that after the fuse had blown, and the ignition was off, I replaced the fuse and the new one blew as soon as I plugged the harness back into the relay.  Replaced the fuse again, and the bike started up fine.  Otherwise, I have been unable to get the fuse to blow without the bike running.

Twice, the bike did not blow the fuse, but when I started it back up almost immediately after shutting it off it ran horribly and the lights were flickering.  After a few seconds of this, the fuse would blow and the bike would die.  Not sure if that's related or if it's a different issue altogether.

NOTE: This was all done with the bike on the center stand and only idling for 30 seconds or so before shutting it off.

I've checked the diode, found that the PO has already bypassed the clutch switch, and I temporarily bypassed the sidestand switch and this did not change the situation.  I haven't been able to locate any shorts or get the bike to act up by jiggling the harnesses.  I disassembled the right hand control, and was unable to find any obvious signs of problems.  One thing I forgot to do was shut down the bike by putting the side stand down in gear a few times to see if the fuse would blow.

I have another kill switch on the way.  If it doesn't fix it, at least it will take one more component out of the equation.

[Drastik]

Replaced then kill switch and thought I was all set at first.  Fuse wasn't blowing for the first three cycles, then started blowing again.  Now that my Haynes manual arrived,  I checked the resistance in the regulator and it didn't match the readings specified in the manual. Also it was erratic when moving the harness to the regulator.  So... A regulator/rectifier will be ordered and we'll see what happens.

[The Buddha]

Goooooooats ... ggggggooooooooaaaaattttttsssssss ...

That's what se7nty7's bike did. Drove him nuts.
Has the bike been lightly crashed on the left side.
If so - you have goats.

Cool.
Buddha.

[adidasguy]

I haven't seen a bad regulator blow the fuse, but possible if the wiring around it is bad and is occasionally shorting to the frame.
Check all your wiring for bad spots and unusual wear.

[Janx101]

I haven't seen a bad regulator blow the fuse, but possible if the wiring around it is bad and is occasionally shorting to the frame.
Check all your wiring for bad spots and unusual wear.

To chime in with Addy

Including slightly discoloured points in the harness plugs ... I've got rid of at least 3 separate elec gremlins in the harness plugs.... Usually slightly carbonised pins and receivers at one place in the plug... And the wires off the back of those blackened pins were discoloured right at the crimp too!

Blown fuses ... Right hand side controls .... The yellow plug above the engine on RHS? ... When I bridged a headlight issue out of that plug... I also cable tied it up higher and onto the frame... Away from the engine heat.... I'm convinced engine heat had a lot to do with the original development of the fault I had.... The plug was not in good condition at all.... And from more than just elec fault heat!

[Drastik]

I'm seeing continuity through the regulator where there should be none (according to Haynes).  That's the main reason I went ahead and sought out another regulator.  I'm thinking it may be allowing excessive current to flow through causing the fuse blow.  The other continuity checks that were erratic seemed to be coming from where the harness connects to the regulator itself (lightly pulling/wiggling that end of the harness changes readings). 

I've seen the term 'goats' several times but didn't know what it was referring to.  I did some searching and found some info.  I'll take a look at the magnets.   

The terminals appear very clean, and I was unable to get readings to change when fiddling with that end of the harness with the multimeter clipped onto the terminals themselves.

Thanks for the info guys.  I'll keep plugging away on this. 

[adidasguy]

Magnets are not going to cause the fuse to blow. If wiggling things around the regulator have been making a difference, check all the wiring there.
Wildly fluctuating voltage hints at a minor short that's coming & going as the bike vibrates. If you think it is the regulator, you can disconnect it and start the bike a few times just on the battery. Then, disconnecting it will move wires so where there could be a short may get moved and no longer short.

Carefully examine all the wiring. Un-do the cable ties. Spread out the wires and examine them. also look for any burnt spots on the frame around where the wires were.

[Drastik]

I wasn't aware that I could start the bike with the regulator disconnected.  I never even thought to try it.  I'll certainly do that tonight and report my findings.

The wiring that I'm referring to that is changing the readings is the 1 foot of harness that goes from the regulator to its 2 connectors (while they are unplugged).  I was performing the continuity test outlined in the haynes manual.

I have yet to find an issue with the main harness anywhere else on the bike either by visual observation or checking for continuity to ground while messing with the harness.  I'm not 100% confident that there are no shorts in the harness, as the PO has clearly done some less-than-professional wiring repairs in the past.  I've redone those 'repairs' as I've found them while unwrapping portions of the harness. 

The thing that's bugging me the most, is that the fuse only seems to blow when the ignition is shut off.  If it were an intermittent short-to-ground in the harness, wouldn't it blow the fuse while the bike is running (when the short occurs), causing the fuse to instantly blow, and the bike to shut itself off?  Currently, I'm not riding the bike.  The fuses are blowing while it sits in my garage, so while there is some vibration involved from the engine running, it's not much because the bike isn't moving.

[adidasguy]

Digital volt meters do sampling at intervals and display the result. A rapid fluctuating voltage can make a digital meter show all wonky stuff.
Analog meters you can see the needle wiggling.
Measuring the output voltage of the regulator with the 2 wires disconnected will give a false reading. It has no load so the regulator can't regulate. It does need to be connected to the battery to properly function.

Think of what you do when you turn off the bike. Are you in gear? Is the side stand down? There is a side stand relay that cuts power to the bike if in gear AND side stand is down. Maybe that combination as you turn off the bike is killing the fuse?

Put bike on center stand. Put in gear. Turn bike on (no need to start it). as you raise and lower the side stand you should hear a click of the side stand relay.

I guess another question is exactly when does the fuse blow? The instant you flip the kill switch or shortly after?

Keep in mind the key does disconnect all power from the bike after the fuse and before it goes anywhere else. The kill switch simply turns off the motor. All lights and indicators should still be on. When the fuse blows, all will go dark. So exactly when does the fuse blow?

If you're in the habit of side stand up before turning on bike and bike off before side stand down, maybe on occasion you put the side stand down before turning bike off and that certain combination blows the fuse.

[Drastik]

Side stand relay is functioning.
Fuse blows instantly upon shut off.

I put it on the center stand, side stand up, in neutral.  Idled bike for 20 seconds and shut off using kill switch. Fuse did not blow.  Repeated process, and fuse blew. Replaced fuse.
Repeated process again. Fuse blew. Replaced fuse, disconnected regulator. Repeated process 5 times. Fuse did not blow and bike idled a bit higher\started faster.

I'm thinking the regulator is shot. Question is.. Is it shot due to a charging issue or is it just a faulty component?

[Janx101]

Think it would have to be a pretty high over charge to blow the fuse...  Far as I know fuses go when there are faults or rapid on/off current spikes .. Like in a short...

You would have to potentially sacrifice another fuse to test the regulator voltage flow ... Start the bike without regulator and check the reading, shut it off and note any fluctuation ....Re-connect it and stick the probes into the back of the reg plug ... Check the reading... Then watch the reading as you shut the bike off to see if there is a big spike? ...

Or just get hold of a new reg and plug it in ... If the problem stops then cool .... If it doesn't, you still have a spare reg!

[The Buddha]

I'm seeing continuity through the regulator where there should be none (according to Haynes).  That's the main reason I went ahead and sought out another regulator.  I'm thinking it may be allowing excessive current to flow through causing the fuse blow.  The other continuity checks that were erratic seemed to be coming from where the harness connects to the regulator itself (lightly pulling/wiggling that end of the harness changes readings). 

I've seen the term 'goats' several times but didn't know what it was referring to.  I did some searching and found some info.  I'll take a look at the magnets.   

The terminals appear very clean, and I was unable to get readings to change when fiddling with that end of the harness with the multimeter clipped onto the terminals themselves.

Thanks for the info guys.  I'll keep plugging away on this.

Dude - what part of "goats" isn't clear to you ?

OK skipping all the jokes.
Your alternator stator is making contact with the rotor. Your drop was on the left side ?
Cool.
Buddha.

[The Buddha]

Here is the history lesson -

http://gstwins.com/gsboard/index.php?topic=54494.msg615328#msg615328

Here is some easy reading on the topic. 

http://gstwins.com/gsboard/index.php?topic=57051.msg646167#msg646167

http://gstwins.com/gsboard/index.php?topic=14715.msg127170#msg127170

I dunno, start checking stator terminals to each other and to ground.

Cool.
Buddha.

[Drastik]

The bike is new to me, so I don't know the history.  My plan was to get it running and use it as my first bike (taking the MSF course early next month).

Quick summary: He purchased the bike in a not running condition a few months ago, took it to a dealership, they did some carb work but said it had 'other' problems they'd need to diagnose.  He is a college student and doesn't have much money or resources to work on it himself, so he sold it to me.

It wasn't running when I purchased it.  I was able to get it running, but it ran poorly.  It was intermittently dropping spark to the left cylinder and wouldn't rev above idle (idled very poorly).  Replacing the ignition pickup and that fixed the spark issue.  Now the bike starts and revs well, but blows a fuse upon engine shutdown.  I can only assume that this issue was present before, but was not obvious because the bike wasn't ran much.

The PO jump started the bike quite often because he didn't have a charger and the battery was dead (jumped from a non-running car battery).  The battery was junk (wouldn't hold a charge after I charged it).  I replaced the battery. 

That pretty much sums up the brief history that I know of the bike.

[The Buddha]

http://gstwins.com/gsboard/index.php?topic=14715.0

Read that - really cool thread from eons ago when we first ran into goats. Complete with starwalt, dgyver, werase and se7nty7 observations. Yea I changed my name to Buddha after Ken called me "Buda" a few times - lame. I know, but it was a recession and that was all I could afford.

Cool.
Buddha. (atleast I spell it correctly  )