'92 FJ died on the road - main fuse keeps blowing!

[Zwartie]

Greetings,

While on a 4-day bike trip with my buddies riding through and around the Huntsville, ON area my '92 FJ died yesterday morning. All started well first thing with the exception that my friend Steve's '03 VFR wouldn't start first thing in the morning due to a dead battery. I fired up the FJ and gave him a boost and we were all ready to roll. There were two other buddies on the ride with an '85 FJ1100 and an '01 K1200RS. We were riding for about 20 minutes in the light rain when we stopped to make a u-turn, discussed where we were going next and when we started rolling again my FJ made it about 100 yards and died. A quick check showed that the 30A (main?) fuse had blown and so I popped the spare fuse in and it started up again. Put the seat back on, ran another 100 yards or so and it died again. Further inspection showed a burned connector located right behind the engine, under the unipod filters. Two of the guys rode to Canadian Tire, picked up a multimeter, crimper, connectors and fuses and I repaired the connection. Installed another fuse and it popped immediately. So then we were on the hunt for a burned/shorted wire and began disconnecting various connectors throughout the bike and testing voltage at the fuse block. The battery voltage is 13.0 volts so no problem there. The other fuses had no voltage across the terminals when the ignition was off, which is to be expected. The main fuse showed 11.45 volts across the two terminals which means you install another fuse and it will blow immediately. Found a large connector under the right side inner fairing cover that when disconnected dropped the voltage across the main fuse terminals to zero. Put in another fuse, turned the ignition key and the fuse blew immediately. It was at this point (about 3-4 hours in) where I decided to throw in the towel. Called my brother in Strathroy (about 5 hours away) and he drove out with his truck and trailer and picked up my FJ along with Steve's VFR which by this time we realized had a bad battery and we drove home. Sigh. So now I'm at home with a Clymer manual in hand ready to pull the fairing off and start some more in depth troubleshooting. Any advice on what may cause the main fuse to blow would be greatly appreciated. Aside from the usual short-circuit stuff, could this be caused by a failed alternator, voltage regulator, stator, CDI...?

Thanks,

Ben Zwart
London, ON
1992 FJ1200
1977 KZ200

[Dan Filetti]

I'm not going to be a big help on your short issue, but you mentioned 'Steve's VFR has a dead battery' and I thought I'd chime in.  There is at least a better than even chance that Steve's VFR has a bad regulator/ rectifier.  If he prompty goes through another battery, the there's a 95% chance it's the R/R.  VFR's are known for this.  Seems like it's a new R/R every ~7-8 years for these bikes.

You may want to pass that along.

FYI.

Dan

[Mark Olson]

Jump starting another bike with the fj can result in  the problem you seem to have. 

you can charge a battery with your fj , just don't crank the other bike with the fj still running and the key on.

this can smoke your rectifier and other bits.     

[Travis398]

Hey Ben, That really sucks.

before you rip the whole fairing off at least check out that short,
Like you said if you're reading voltage across that blown fuse there is a short and will only blow another fuse.
you could probably put a test light across the terminals somehow and start disconnecting plugs till the light
turns off (or meter reads 0) to see if it will clear. the pieces you mentioned have plugs to disconnect.

didn't Randy (or someone else?) have a brake light wire short out?
and kill the bike. so maybe a wire is shorted to the frame somewhere.

anyways I'll stop rambling and let you get back to it
good luck,
Travis

[Zwartie]

Update:

After taking a closer look at the schematic in the Clymer manual I see that the digital clock runs off the main fuse circuit. What does that mean in terms of troubleshooting? It explains why we were reading 11.45 volts across the fuse terminals with the key off. As soon as you connect the meter across the fuse terminals you are completing a circuit from the battery positive side to the clock and back to ground. So between the impedance of the clock load and the high resistance of the meter you have a simple voltage divider which explains why you get most, but not all of the 13 volts across the meter leads. It also explains why after we disconnected one of the harness connectors under the fairing, that voltage dropped to zero - we had likely disconnected the clock.

Yesterday I took the upper fairing sections apart to have a better look at things and of course found nothing obvious. I called Mark from LGL (formerly London Generator) to discuss and he said he would like to look at the schematic and also offered to lend me a 20A breaker to help me troubleshoot. I connected the breaker in place of the fuse last night and the bike roared to life. I had also checked the rectifier and it tested out good. So I may be stuck with a wet-weather anomaly. My next step is to inspect everything that is connected through the main fuse for obvious signs of corrosion, arcing, etc... If that doesn't produce anything obvious it may be time for a spray-down test with the garden hose to see if I can simulate the problem. Oh, and I'm going to get a CAA membership in case I find nothing and need the bike towed in the future!

Ben

[SlowOldGuy]

Perhaps this will be a bit too much of a sledgehammer approach.

But, if you're convinced that it's just a short and all the expensive stuff is not the culprit then install a larger fuse and wait for the smoke to show you where the short is.

DavidR.

[SkyFive]

Perhaps this will be a bit too much of a sledgehammer approach.

But, if you're convinced that it's just a short and all the expensive stuff is not the culprit then install a larger fuse and wait for the smoke to show you where the short is.

DavidR.

I did that one time with a over amperage circuit breaker in place of a fuse, I did find the short but it took me three days to repair the other melted wiring.

[SlowOldGuy]

So you got it fixed in 4 days?
Is that better or worse than spending a month tearing everything down trying to find a short?

I'll admit that it's not the elegant solution, but it is an effective "last ditch" effort.  The key is avoiding/minimizing collateral damage.

DavidR.

[Pat Conlon]

All right I'm calling the cops...WHAT HAVE YOU DONE WITH DAVID!!! WHERE IS HE?  DO YOU WANT MONEY?

Perhaps this will be a bit too much of a sledgehammer approach.

But, if you're convinced that it's just a short and all the expensive stuff is not the culprit then install a larger fuse and wait for the smoke to show you where the short is.

DavidR.

[SlowOldGuy]

Relax, Pat.  I never said I would do it on MY FJ!  :-)

DavidR.

[Zwartie]

Update: Problem Solved!

After about 4 hours of troubleshooting today including full removal of the fairing I located the source of the problem - the blue wire feeding the right side marker / signal light had the insulation worn to the point where the wire was making contact with the fairing frame and thus shorting out to ground. One thing that really helped the process was using a 20A breaker in place of the 30A fuse. I would have gone through a couple dozen fuses otherwise. It also helped to bypass the ignition switch and jumper out the connector so I could narrow the problem down between the ignition system and lighting.

Thanks for your help!

Ben