[sdphill92]

Ok so I was on my way home from work last night on my 1986 vn750 and out of nowhere the bike just died. Nothing had power at all (no lights nothing). I cycled the key a few times and got nothing so I checked out the battery and couldnt find any problems there. My next instinct was to check the fuse box. The 30A main fuse was blown, So I grabbed the spare 30 that was in there and stuck it in and i instantly watched it pop. So I decided to call my friend to bring his trailer. While I was waiting I started looking at connections. The plug on the lower right side of the junction box appeared to be not in all the way. I pushed it in about a quarter of an inch and then grabbed the 10A fuse from the headlight and it I had power again. Being 2 miles from home I thought Id gun it and try to get home. I got about a mile before it died again and the 10A was cooked. So my friend towed it home for me and I stuck it in the garage. Now this morning I woke up and I stuck a 30A in the Main position and everything worked fine. After some reading I removed all the fuses from headlight, taillight, etc and put them in one at a time and turning the bike on to see if it would pop with certain fuses in. I loaded all the fuses in at once and it still started without problem. I have been unable to do a street test because it has been raining like an SOB all morning but I did put it in gear in my garage, also revved it and there doesnt seem to be a problem. I know the real test will be riding it but I'd like some input. Here is some backround info of what has happened since I got it a few months ago.

One night on the way home from work my headlight quit working. It ended up being the fuse, then it worked fine till the next day and the actual bulb burned out. I replaced it and about 3 weeks later it burned out again both hi and low. I replaced it a second time and it has been a little over a month so I am telling myself I probably just got a bad bulb the first time.

I replaced the battery about a week and a half ago, it appeared older and the new one seems to work fine.

I just replaced sparkplug wires about 2 weeks ago because they were the original wires and the guy I bought it from had them taped together and at night you could see a couple of them arc on the cylinder.

I replaced the tail light bulbs about a month ago with LED bulbs.

One weird thing that happened was about 4 or 5 days ago I was coming home from work and I looked down and my RPM, Gas Gauge, temp gauge, and lights werent working (thank god it was day time). I also tried the horn and it didnt work. The only thing that worked was the speedometer. So I pulled of the main road I was on and to a less busy back road still riding and I wiggled the key, and after a few seconds I had power to everything again. I examined it when I got home and the key didnt feel sloppy or loose. It has only done that the one time.
So theres all the background information. I know some or all of it may be irrelevant but I thought I would be thorough. I am mechanically inclined but I am new to the motorcycle world and I also dread electrical troubleshooting. Like I said I havent taken it on the road today yet but everything appears to be functioning fine.

 

[sdphill92]

also

I guess what Im asking is, is it possible that the plug that goes into the junction box (bottom plug) being loose could have caused the problem? The reason I am not sure is today I unplugged it completely and turned the key and it was still fine.

 

[dariv]

Loose plug shouldn't blow a fuse.....
You seem to have a short, probably an intermitant one.... I would guess around the neck where the connectors are on the left side or around the ignition switch.
Pay particular attention to the white wire and the brown wire....

 

[sdphill92]

Yeah I didn't think a loose plug would pop the fuse. When you say around the neck I'm assuming that you mean the plastic covers in front of the gas tank that are held on with a couple screws right?

 

[WilliamTech]

Yeah I didn't think a loose plug would pop the fuse. When you say around the neck I'm assuming that you mean the plastic covers in front of the gas tank that are held on with a couple screws right?

Yes
Also, when you wiggled the key, lights/tach came back on......
I might suspect the Ignition Switch contacts.... I've read on forum of others with similiar issues, and Ignition Switch contacts were suggested.
hope this helps
WilliamTech
:smiley_th

 

[Kelly2001]

Your R&R may be going south and going overvoltage when hot- this could cause a blown main fuse and blown headlights. Get one of these to keep an eye on things real-time. I have one and it works great. I ran a relay and a 10-gage wire directly from the battery, up close the the monitor wires.

http://roadstercycle.com/Motorcycle voltage monitor.htm

 

[shark88]

Mine shorted the 30A main when I first got it due to the wires where it comes up around the neck into the headlight bucket, a wire rubbed through and was touching the frame. Taped it up and no more problems.

 

[kc2dgq]

I agree with Dariv that a Loose plug shouldn't blow a fuse.....
but...anything is possible.

I don't know how mechanically inclined you are or if you are handy with a voltmeter, so here is my first suggestion to shotgunning the problem:

If it were me, I would check all connections and wiring. Inspect the connections for clean and secure contacts and look for chafed or exposed wiring.

Then pull all the fuses.....start inserting them one at a time AFTER the bike is warmed up and while the bike is running you should turn the handlebars left and right to see if any of the fuses fail. also poke around and wiggle the harness while doing this.

It is probably the quickest way to isolate a chaffed wire or a short in the harness if that is the problem.

If nothing reveals itself, you may just have to ride it and see how it goes. there is an outside chance that the loose connector was the sole cause of all mentioned....but it is a slim chance at that.

 

[sdphill92]

ok

Thanks for the suggestions. Im definately going to try the moving the handle bars and pulling on the harness. Im pretty inclined as far as Im not afraid to tear it apart and search every inch of wire on the bike. As far as the voltmeter Ive got a few friends that are electricians. I really want to pinpoint the problem. I got lucky this time I was 2 miles from home. I work 20 miles away. Dont wanna be broke down on the side of the freeway.

 

[dariv]

...Your R&R may be going south and going overvoltage when hot- this could cause a blown main fuse and blown headlights....

headlight maybe, but not main fuse... I believe they are rated 32VDC.... and besides, with over-voltage you should be drawing less current. :motorcycl

 

[Kelly2001]

headlight maybe, but not main fuse... I believe they are rated 32VDC.... and besides, with over-voltage you should be drawing less current. :motorcycl

Sorry, that's not correct according to Ohm's law: I=V/R. Current increase is directly proportional to voltage increase.

 

[dariv]

Humm.... Guess I was half asleep when I wrote that :drool:
I was thinking about the current required to deliver a certain amout of power. If I need 12w of power I could use 12 v at 1 a or 24 v at 0.5 amps.
Good catch. :smiley_th

 

[sdphill92]

Well I spent most of the day going over all the wiring I could find, had the tank off as well as the headlight, the handlebar gauge assembly and many other pieces, couldnt find a short. I also turned the key on while I had everything apart and pulled on every wire I could find and still no problem. I put it back together and rode it. Now its fine.... I dont know what would be worse. Finding a problem, or the problem magically going away. scary!

 

[new rider 9984]

check the wires to your r/r my connector was loose and the brown wire touched the black one and my main fuse blew

also on my front turn lights the leads were extremely long and kept pinching up blowing my tail light fuse i just shortened them i think i cut out about ten inches of wire so it stayed high enough to stop pinching in the fork stop