Blowing fuses upon install with key in the "off" position

[Lazer400]

Hello,
I am new here and new to the xs400. I recently purchased a 1980 xs400, it ran good, started up second kick after sitting all winter. I have been riding it all week.
The bike had been "customized", gauges are gone, indicator lights are gone, turn signals are gone. The PO told me that there was a short in the ignition somewhere and in order to keep the battery from dying I needed to disconnect it when not riding.
All was fine until I decided to replace the OEM tail light. I finally got it to work after blowing a handfull of fuses. Any way, I got it working just fine, went to start the bike the next morning, and nothing. The issue is that the main fuse blows upon installation even when the key is out. what the hell? So far, I have disconnected the new tail light, the headlight and it is still happening. I have taken the tank off and thouroughly inspected the wiring for abrasions and other signs of a fault. It will even blow a 30a fuse. I am wondering if these are signs of a bad ignition switch, or perhaps something else? I am stumped and just want to ride in this nice weather we've been having.
Other points of interest: The fuse box was replaced at some point, the head light is on a basic on/off switch any ideas???

Thanks,
Tom-

 

[HoughMade]

There's no shortcut on this one. Clearly your wiring harness has been thoroughly butchered. It's even to the point where I don't know how much use the stock wiring diagrams will be.

All you can do is trace every wire one by one and look for a short.

 

[226dark]

There's no shortcut on this one. Clearly your wiring harness has been thoroughly butchered. It's even to the point where I don't know how much use the stock wiring diagrams will be.

All you can do is trace every wire one by one and look for a short.

Welcome! No simple shortcut solution, agree.
You thoroughly checked wiring for abrasions, but look close for areas in the main harness where the previous owner black-taped over and have a look for any shorts there.
And why would something be drawing current when the ignition is off???
Do you still know the PO and what he did with wiring the ignition?
No shortcuts true. Prob not recommended to see if a 30 amp fuse will blow.

 

[jmd_forest]

Also check for short in the ignition switch, not just the wires.

 

[drewpy]

I'd just start again, and do it properly.

 

[Lazer400]

Well, crap.
I was really hoping that you would've all said "those darn ignition switches"
It is kind of funny thoug, right when I logged in the page was on re-wiring tips.
I have looked the bike over again and again but still have not found the fault.
I am going to order a new ignition switch when i am done writing this post.
It is just strange that it would be blowing fuses with the key off and out of the switch.
The previous owner was not the one who "re-wired" it, but he was definitely aware that there was a short some where in the ignition system. I figure, the switch is only twenty bucks and I wouldn't mind replacing it even if it isn't the problem.
I do agree that the wiring diagrams in the haynes manual aren't going to be dead on, but that is all I've got. This is frustrating, I just had it in good working order and now i'm stumped.
If you all can think of anything else let me know.
Otherwise I will check back after the new switch is installed.
Thanks again for the help!

Also, the fuse box had a lot of bad sauder eveywhere but I have since cleaned it all up and made proper connections, still nothing.


Tom-

 

[Lazer400]

Okay, here is an update. I did not order the switch. Instead, I went home and hit it hard with the diagram and multimeter. This is what I have come up with....The ignition switch (main switch) is good. The stock fuse box was replaced at some point with a blade style box. and the stock box gives the main (reds) circuit it own closed circuit. This partcular box has seperate "ins" but common "outs" if that makes sense. As a result, all circuit were always hot because the Main "in" is connected to the battery. So, I disconnected the main "in" from the box and wired it directly to the ignition switch through a 20a fuse. doing so has stopped the fuse from blowing with the main switch off. First problem solved. I then removed the branch circuits by removing the R/y and R/w fuses. This leaves only the circuit running through the brown lead between the ignition and the fuse box. I cut the brown wire after the Ign. switch and all is as it should be. This leaves only the brown from after the switch to the fuse box The only things coming off of that section of the circuit is first something that is unlabeled in my diagram. It looks like a small coil right next to the AC generator it then runs to the voltage regulator. Anyone have any Idea what this "coil" is? is it part of the generator??
So, basically I have the "coil" and the voltage regulator left to test. I will also mention that I am looking at the G and SG model Haynes diagrams. Also, the blue coming off of the ign. switch is only running my head light, License plate and tail light. all of which have been disconnected in the process of elimination.
Any thoughts?? I feel like I am close.
Also, When I reconnect the brown at the switch and turn the key it sounds like thew battery is boiling? and there is no juice coming through back to the brown at the box. This just happened. Maybe I really blew whatever was weak to begin with.

Thanks,
Tom-

 

[drewpy]

the small coil will be the field coil this creates a magnetic field for the stator to work and is fed from the voltage regulator.
The voltage reg varies the amount of current going to the field coil to stop the battery over charging.
the rectifier could be earthing out!

 

[Lazer400]

the small coil will be the field coil this creates a magnetic field for the stator to work and is fed from the voltage regulator.
The voltage reg varies the amount of current going to the field coil to stop the battery over charging.
the rectifier could be earthing out!

Thank you for the clarification on the field coil.

In The diagram it looks like the field coil is first and runs to the Vol. reg. then to the fuse box. with a G wire completing the circuit. My thought is that maybe there is a short at the field coil or the voltage regulator as they are next in the circuit, or within the wiring. Hopefully within the wiring or clips. Would the rectifier grounding out make the battery boil??? When I turn the main to "on" the voltage goes really low, this is new, as it was getting power all the way back to the Brown at the box. I don't have the diagram in front of me at the moment but I will see where the rectifier comes in and check it too.

 

[Lazer400]

I will also mention that When I was riding last week, I noticed the headlight would dim while I wasn't riding and then brigten up with the throttle. It seems like this could be due to a faulty volt. Reg.
What do you think??

 

[drewpy]

sounds like its struggling to charge. are you getting 13 - 14 volts @ 3k revs?

make sure you have a sound battery.

switched live to fuse, then voltage reg, then field coil.

stator is charging when engine runs and field coil is activated!

its simple and no moving parts apart from an electro mechanical volt regulator (later electronic)

 

[Lazer400]

I definitely have a short somewhere. It isn't even blowing fuses at this point. I turn the key on and voltage tester goes dim. Tested the rectifier, volt. reg. and the connection to the field coil. Battery is good, holds a charge for quite some time and the readings are good too. I cannot start the bike at this point to test the voltage while running at 3000k.
I will though, that before it started blowing fuses it was charging just fine.

 

[Lazer400]

Drewpy, Upon cruising the web looking for related information, I stumbled across a thread on yamahaclub.com that you had posted on. It is called "minimalist wiring 82 xs400"
I was wondering if you had a wiring diagram, or maybe know of one of a minimalist type that would be applicable for an 80' xs400 G SG.

I am thinking about just starting over and creating a new harness. At least then I will know what is what. I just need a basic setup that has all of the necessary electrical components.

Thanks.

 

[226dark]

Of course he does.
And here's more interesting leisure reading.
http://www.xs650.com/forum/showthread.php?t=61

 

[drewpy]

just check out my tracker blog, all the info is there (tip, its on the front page of this forum too!)

 

[Lazer400]

Awesome. Thanks.
Well, I am going for it. All new, simplified wiring. I figure even if I get to the bottom of the problem, I will end up wanting to clean it up anyway.
I am still going to say that there is a short in the system somewhere, but who knows where. It seems like the amount of time it has taken me to get this far, I might as well just do it right.
That is a sweet tracker there Drewpy.
I will post pics of mine when I get a chance.

Thanks everyone for the help. I will check back in here when I am done.


Tom-

 

[jmd_forest]

There's no magic to tracking down electrical problems: methodically disconnect 1 component at a time, test for your short or open, reconnect, and on to the next component. Go through all of the components, unless you are absolutely sure the first problem you find is the last problem. It can be tricky sometimes, but a logical, methodical approach usually works.

 

[Lazer400]

And why would something be drawing current when the ignition is off???


Dark,
The bike is drawing a current when "off" because the fuse box was replaced with a blade style box.
More specifically, the blade style box Has all separate "ins" but all common "outs".
What was happening was that the Hot wire feeding into the ignition switch was always in contact with the accessory wires on the "out" side of the box. There for it was actually always on. the only thing that the ignition was doing was turning the lights on or off.
I fixed it by disconnecting the hot (red) wires from the fuse box and connecting them to their own fuse.

Figured I should put this info in here somewhere in case some one else is dealing with this problem.

Also,
I have drawn up a simplified wiring diagram I will post it here when I am finished, as well as on the diagrams thread.

 

[Lazer400]

Alright, I need just a little more help.

Since my last post I have completely taken out the wiring down to each component and started fresh.

I am running head and tail lights on their own circuit, and ignition and charging systems on the other.

The lights circuit is good to go.

My issue is that now I have no spark at the plug. I have power to the coils but no spark.
My wiring is good and voltage to the coils is reading normal according to haynes.

I have the electronic ignition system with the TCI unit and pick up coil rather than points.

I have power to all connections except the w/g and w/r wires running from the pickup to the tci. I am assuming that the b/w supplies power to the pickup and when the rotor spins it powers the w/r & w/g sending a signal to the tci, which then sends amplified power to the coils. Is this correct?

Does this sound like a faulty TCI to anyone?

My first thought was that the coils were bad since there was no power to the plugs.
I am now leaning towards TCI because I have power to everywhere it should be but the message never makes it past the TCI and to the plugs.

Also when testing for spark I DID ground it to the engine and still nothing.
I Also tested the windings on the coil, the secondary was a little high but it was also really cold in my garage. The primary was good right about 4ohms.

Battery is reading 12.5 and after cranking the electric start a few times it drops just a little bit. No lower than 14.7 before I recharge.

I have power to the coils, power to the TCI and power to the pickups but no spark.

Any thoughts??


Thanks,
Tom-

 

[ThePsuedoMonkey]

If I am reading the wiring diagram correctly, then the TCI connects to the coils, pickup coil, and the kill switch, which connects to the ignition fuse, followed by the ignition unit, then power.
To be honest, it seems odd that the TCI would just stop working, so I am more inclined to look for a bad connection.