Topic: Help me trace this wiring issue

[Scott S]

 I posted in a thread about a possible bad ignition switch. I don't think that is my entire problem, if it was, in fact, the problem at all. Here's the thread:

http://forums.sohc4.net/index.php?topic=122136.msg1383713#msg1383713

 I was doing some carb tuning the other day and the bike went from running to dead. It would power up with the key on, but before I could hit the start button, it would blow the main fuse.
 Replaced fuse, blew it again.

 Thought maybe the piece of crap Emgo ignition switch was the culprit, so I cleaned and tested the original Honda switch. It was dirty, so I cleaned all the contacts and reassembled. Nothing broken inside or iffy looking otherwise.
 I can test it can get resistance across the two prongs that supply power when I turn the key. Turn the key off and the circuit goes open. I'm taking that to mean the Honda switch is good.

 Installed the Honda switch and blew fuse #3.

 I have power to the starter solenoid.
 I have power to the main fuse.

 When I test the red wire that goes from the main fuse to the ignition switch, I get an open circuit...infinite resistance.

 The fuse block on the bike has some melted plastic on the holder. It was like that when I bought the bike, so this problem has been around for a while, I think. I remember blowing a couple of fuses when I first built the bike, but I then put hundreds and hundreds of miles on the bike without any trouble.
 Only recently, when I posted about the "bad ignition switch", did I start having trouble again. Whatever has been shorting out has appeared to have finally given up the ghost.

 I'll pull the headlight bucket and look for anything obvious, but where's a good place to start?
 I have buddy with a professional master wiring kit. We talked about making a new main, red power wire with the correct connector and just run it outside the main loom and up to the ignition switch. Thoughts?

 Oh, and I WILL be making a new blade style fuse box, too.   

[Scott S]

 Nothing? Am I way off base here?

[bollingball]

Oh, and I WILL be making a new blade style fuse box, too.

I would start there with a temp inline fuse to go around or by-pass the one you have now that shows melting.
Ken

[Xnavylfr]

If I'm reading correctly!! when you test resistance on the red wire to ground you get INFINITE resistance,,, That would tell me the circuit is closed not open.

If your VOM has a continuity, check with that setting. It usually  shows a bell or a buzzer if the circuit is open nothing happens, if it's closed the buzzer/bell will sound.

Xnavylfr(CHUCK)

[Scott S]

 Mine doesn't have a bell or buzzer.
 I'm not the best with electrical and, certainly, electrical terminology. I get no reading across the ends of the red wire from the main to the switch. I do have one of those battery powered test lights. I can try that and see if the bulb lights up. If so, the wire is intact. If not, the wire has failed, right? Same thing as checking for continuity with the buzzer.

[bollingball]

Mine doesn't have a bell or buzzer.
 I'm not the best with electrical and, certainly, electrical terminology. I get no reading across the ends of the red wire from the main to the switch. I do have one of those battery powered test lights. I can try that and see if the bulb lights up. If so, the wire is intact. If not, the wire has failed, right? Same thing as checking for continuity with the buzzer.

Yes if the bulb lights up the wire is good. But with that test you are verifying voltage. The meter is better for that because it will tell you how much voltage. It should be the same as your battery voltage. Just put the meter on 20vdc scale. Can you post a picture of the meter? or if not tell us the name and model #.
 With the ohm meter on if you put the red and black lead together the reading you see is the same or very close to the reading you would see if you were testing a good wire. Leave the meter on and separate the leads and that is what you will see if the wire was broken.
Ken

[lucky]

What made you think the ignition switch was at fault?
The title of your thread is "Help me trace this wiring issue".
I would have said, Can you please help me with this wiring issue. Just saying.

"I was doing some carb tuning the other day and the bike went from running to dead. It would power up with the key on, but before I could hit the start button, it would blow the main fuse.
 Replaced fuse, blew it again."

I would not suspect the ignition switch at all.
You said it will "power up" but before you could hit the start button it would blow the main fuse.

Then you put in a new fuse and it blew the fuse again.

To me that is solid proof you have a short circuit.


Try this:

Remove the ignition switch completely.
Now put in a new fuse.
IF the fuse blows it means the ignition switch is NOT at fault. Simple.

[Scott S]

 Did you click on the link? I posted a video about a short I had and it was the consensus that the switch was bad.
 I also posted that I don't think it was the switch and that I believe I have a short. I'm asking help on figuring out how to narrow down where the short is so I can find it and repair it.

[Don R]

Are you checking volts red wire to ground or at both ends of the red wire?

[Scott S]

 Yes. I get 12 volts to the red wire at the starter solenoid and at the main fuse, but not up at the switch.
 I haven't had time to work on it in about a week. Hope to get back on it on my long off. I'm pretty sure now there's a break or dead short between the fuse and the switch. Just have to figure out what to do about it.

[Gregorymoto]

The fuse blows when you hit the starter?
Will the bike fire up and not blow a fuse if you kick it?

[Scott S]

 No, the fuses blew when I turned on the key. I could see the neutral and oil lights light up briefly the first two times, then go out. The last time/third fuse....nothing at all. I'm getting no power to the front of the bike, at least not the places I've checked so far.

 I'll pull the headlight to make sure there's nothing grounding out in there, but I'm thinking it's something in the harness between the fuse box and switch.

[lucky]

I am trying to help you.

I would unplug the ignition switch from the harness
and then put in the main fuse.

If the fuse blows the ignition switch is not at fault.

You said that right before this problem occured you were working on the carbs.
Did you remove the gas tank?
If so one of the coil wires could be touching the gas tank or frame.

[Scott S]

 Carbs were not removed, nor was the tank.
 I'll check all of these things ASAP.

[Scott S]

 Well, I found this yesterday. Notice anything funny?







 The heavier gauge red wire coming from the battery doesn't match the red wire on the fuse holder. That's also the fuse that is blowing and the holder was melted when I got the bike. Would the smaller wire be enough to cause that holder to melt?
 
 I can't just flip it over, as the connectors are made to go together one way.



 The middle wire is correct. If I can get the end wires out of the holder, I'll flip them, cut off the fuse box and replace with blade style fuses. If not, I'll get a new molex plug and make new fuses.
 There is definitely something up with the fuse holder that holds the main fuse sends power to the switch. I'll fix this first and go from there.

[Scott S]

 Well, I repaired/replaced the fuse block by installing new blade style fuse holders onto the stock plug. I pushed out the wires, cleaned them and installed them in the correct order.

 Tested everything from the battery to the switch, including the RH control, headlight, ignition switch, etc.

 Installed a fuse, turned on the key and promptly blew said fuse.

 Pulled the points cover (aluminum finned type) and found a squashed, pinched wire on the Pamco...DOH! I rode the bike for several miles with the cover off while I was checking/setting timing. I realized today that I didn't start blowing fuses until I installed the cover. I guess the wires were pinched enough to contact each other or make a ground.

 Skinned back the sheath and checked the wires. Separated them from each other and...voila!....the bike would start and I didn't blow any fuses! Checked for spark and I'm getting spark from both coils.
 Used some liquid tape to repair the wires.



 The bike is running now, but I'm still having carb issues. On to the next task!