Topic: No longer blowing fuses, Still no headlight tail or starter..

[nowhere_fast]

So last night on my way home from work.. poof, electrical goes out on me. pulled over, realized i had a blown main fuse. replaced the fuse, blew instantly again. i also noticed the fuse block and wiring harness were getting very hot very fast.  i got the bike home, took apart the fuse block, as i had noticed some corrosion and melting in the main. i then re-soldered my main wires into the spot designated for the spare, put in a new fuse and turned the key.. now i have neutral light, oil light and rear turn signals. No headlight or tail light. No heat anymore from the wires or fuse block. i tried starting the bike, got a very weak crank and that was about it.  I also noticed when i turn my key to the parking lights, it instantly blows main fuse. im about ready to head-but the sidewalk..  any help would be greatly appreciated..



Just got it to start.. had to press the starter a few times, but it fired right up after a few little clicks.. but still no head or tail lights!! what could this be??

[Johnie]

Tell us what bike you are talking about here...

[TwoTired]

Tell us what bike you are talking about here...

Yeah, that might help.

Also tell us where in the fuse its blowing, near the ends or in the center of the fuse?

[nowhere_fast]

its a 76 cb750f (F1)  The fuses are blowing in the dead center, which, i know is a sign of a short somewhere. But i checked the wires, and recently went through and soldered and shrink tubed all of the wires under the seat for that very reason.. But the fuses now only blow when I turn the key to the parking lights.

[333]

I'd check the back side of the ignition switch.

[worlddrum13]

[/quote]


Also tell us where in the fuse its blowing, near the ends or in the center of the fuse?
[/quote]

ive never heard this trick before.. sounds useful! what are the symptoms of blowing fuses in different spots?

[OldSchool_IsCool]

Also tell us where in the fuse its blowing, near the ends or in the center of the fuse?
[/quote]

ive never heard this trick before.. sounds useful! what are the symptoms of blowing fuses in different spots?
[/quote]

Blowing in the middle is due to an electrical short or over-current somewhere.  Blowing (or more accurately MELTING) on the ends is an indication that your fuse clips are loose and/or dirty causing excessive heat on the fuse contacts.

[nowhere_fast]

Im not very good at this electrical stuff.. so correct me if im wrong, but I assume if its a wire shorting out it would blow the fuse instantly after turning the key right? Its only blowing the fuse when i turn the key to the parking lights.  Yet I have no lights when put the key to "on" and the starter button doesnt work unless you push it about 10 times..

[OldSchool_IsCool]

In stock trim, the key in the P position turns on the tail light only.  That would be a good place to start looking, though I suspect you have more issues than just the tail light.

Here's a trick.  Pull you main fuse and put a 12v light bulb across the clips instead.  When the light is burning brightly, there is an active short somewhere.  Now, jiggle your wires.  If the light goes out or dims significantly, then the wires you were wiggling prolly has the short. 

If you can't get the light to dim by wiggling wires, try to unplug connectors.  Again, when the light goes out or dims, that connector will lead you to your short.

Here is an excellent site to help explain Honda motorcycle wiring.  You can turn off systems that are uninteresting, letting you study one system at a time.

http://oldmanhonda.com/MC/wiring750K1.html

[TwoTired]

Also tell us where in the fuse its blowing, near the ends or in the center of the fuse?
[/quote]

ive never heard this trick before.. sounds useful! what are the symptoms of blowing fuses in different spots?
[/quote]

A fuse will melt due to the increased heating caused by over current through a resistive device.  The fuse does have some small resistance.  Most fuses are thinner in the middle so a true over current melts at that point and is plainly visible.   However, the closer the fuse carries current toward its rated limit, the warmer it will be.

The end caps have more mass, and when all is well they wick away (radiate) heat ,keeping the ends cool during an over current event.

However, if the fuse clip contacts become resistive, as in an oxidation film, that resistance generates heat and transfers it to the fuse end cap. adding that heat to the heat generated by the fuse element.  When the clip heating becomes excessive, adding to the heat of the operating fuse, the element melts near the end cap, near the causal source, even if the actual current rating is not exceeded.

There is an added heat generation source, that of vibration, such as that created by an operating motorcycle, particularly at high RPM.

On top of all that, when the engine is revved, so is the alternator which is trying to increase the voltage at the battery to 14.5V.  All the resistive devices on the motorcycle draw more power as the voltage increases, which ALSO draws more current through fuse AND any oxidation on the fuse clips.

In some cases the fuse block has been allowed to operate in a deteriorated high heat situation, which can melt the solder on the back of the fuse block.  The resulting narrow electrical pathway generates heat which is conducted through metal wires outward from the source.  And, the fuse end cap is fairly close by.

Maintaining the fuse clips in like new condition will greatly extend the useful life of the fuse block as well as the reliability of the entire machine.

Cheers,

[nowhere_fast]

So I tried the lightbulb trick, it didn't illuminate the bulb at all.. removed the seat, fiddled with some wires and was able to get a brake light when brake was engaged, and when I put the key in P i could get a tail light. no blowing fuses. yet i still have no front or tail when key is "ON."  Nor do i have a starter.. this is beyond frustrating!! thanks to everyone for replying though so far, i REALLY appreciate it!

[OldSchool_IsCool]

Yes, sure sounds frustraiting.  Take it slow.  Be methodical and trace one circuit at a time.  Say pick you starter and forget the other systems until your starter is working again.  then move on to the next system.  Take on the trees one by one, not the whole forest.

[nowhere_fast]

So after checking the fuse box with a meter i have power going to the main but no power to the tail or head.. What would cause this? I know everything is wired correctly, because everything functioned properly before this happened. When i hit my turn signals my head light and tail light blink as well.  Would this be caused due to the front turns also working as running lights? And if they blink, are they getting power? ANY IDEAS?? ANYONE?

[DarcyCB400F]

After a quick read of this thread, I wonder if your starter switch is your problem? The headlight circuit goes through the starter switch and if you have to "press the starter button 10 times" perhaps this is your problem??

Im not very good at this electrical stuff.. so correct me if im wrong, but I assume if its a wire shorting out it would blow the fuse instantly after turning the key right? Its only blowing the fuse when i turn the key to the parking lights.  Yet I have no lights when put the key to "on" and the starter button doesnt work unless you push it about 10 times..

I would take it apart to have a peek. But be careful, when I took mine apart, I found out it was faulty when I was left with a palm full of little broken bits that used to be the guts to the starter switch...

With it all apart, I was able to jump the wires to get the headlight to work and the bike to start... just not both at the same time.

[nowhere_fast]

IT WAS THE DAMN STARTER SWITCH!!!! as bummed as i am that i tore the whole bike apart to figure it out, im really happy i found and fixed the problem! thank god for friends that own a motorcycle salvage yard with about 20 CB's haha .. thank you to everyone for your advice every little bit helped me along the way! i owe you all a beer or 10..