how do you find which wire is grounding?

mitchberry · Dec 28, 2009

long story....

very aggravated...

before i get into this, i'll put the question.......

How do you locate / figure out which (if any) wire is grounded out with a volt meter? Specifically, i mean one that SHOULDNT be...

-----
Everything worked great the other day, so as to be expected, it doesn't now.

I don't have a battery yet, (in the mail with everyone's late christmas presents that have yet to arrive) so i'm using my charger to test things out (on my 69 suzuki T500 for the newbies).

When i plug the charger to the+/- battery wires, the charger clicks off pretty much immediately, then tries again a few seconds later..... "click click click click click click" and will keep going indeffinitely.

typically when that happens it means there's a ground in some wire..

i've gone over that |) /=\ /\/\ |\| |E |) thing with a fine tooth comb; through every square mm of it. it is all there... all good...

The one problem i was having though was the switch on the bandlebars. It was corroded, crapped up, and didn't work. this caused all sorts of issues with the lighting, but once i figured out the problem i was able to test around it and make it work temporarily.

I did exactly 3 things between the time it worked and the time it started doing the "click" thing, besides let a few days get between it.

1. moved the blinker relay to where it goes originally.
2. tightened the bolt that holds the rectifier onto the frame (considering that is where the blinker relay goes; on the other side of the rectifier, secured to the frame) i didn't OVER tighten it though.. i'm deathly afraid of breaking it since they seem to be very difficult to come by.

3. yanked the switch off of the old bars, and out of the light bucket to make way for the new bars and switch.

The obvious first guess would be that the switch being disconnected is causing these issues.......

that shouldn't logically be the case though. The bike should in theory be able to run without lights, horns, or blinkers, much less a switch to control them. but CAN NOT run without a battery.

The other thing is, if i bypass all of the other **** and go straight to the switch with the +/- from the charger, everything works.. well..... sorta....

it isn't until i go behind the KEY when things start screwing up........

but........... if i UNPLUG the ignition switch, and go to the rectifier, the same **** happens. it's all kinds of dn-pӘʞn╛

Not really sure what to do at this point.. i think i'm ready for bed. tomorrow i may pull the entire harness out and search again for any grounded wires that shouldn't be, and cut the rectifier out and make sure it didn't get screwed up somehow.

Any thoughts?

Wiring is my -least- favorite part of building bikes at this point

benny hedges · Dec 28, 2009

i think you have the right idea - leave it, have a think & come back fresh.

could be anything tbh so quite pointless saying it's this or that.
obvious starters are the corroded switch on the bars, the ignition switch, and maybe the rectifier is supposed to have an insulator between the frame???
could be a worn bit of the harness where its been chaffing against the frame for years - mainly around the headstock and under the tank.

good luck anyway lol

just take your time and don't lose hope!
it's bound to be something simple.

slumlord · Dec 28, 2009

2 ways to test the ground

First,let's say that you have a complete circuit and need to determine which of the 2 wires is the ground wire. If you took a standard test lamp and put one wire on the ground and one wire on hot,it would light. Reverse them and it still would light
If you do the same thing with a 12 volt LED light, the light will illuminate only if the hot lead to the light touches a hot wire.By the process of elimination you identify the ground wire. So,I guess you could pigtail the hot lead of an LED to the + battery or +charger and search for a ground with the grounding lead. I like LED because even with a 2 amp charger input,they will light brightly
They also make the old style test lights with the needle probe and some of them have a feature of the test light lighting different colors depending on whether the needle probe touches a hot or ground wire.
Now let's say that you located a ground that is right in the heart of a bunch of wires in a wiring harness. Instead of digging into the harness,it may be much better to run a new wire outside the harness than to cause even more problems with the old brittle wires.

benny hedges · Dec 28, 2009

slumlord said:
old brittle wires.

i think this is the problem.
plastic insulation when this bike was made isn't the same as the material as used today

i would suspect the insulation is cracked and broken like snakeskin under the tape.
could be gone in a thousand places - depends how the bike was stored?

primalmu · Dec 28, 2009

To answer your question, place one of the multimeter (on resistance/Ohms setting, with the battery DISCONNECTED) probes on a grounded point (frame, though the best option is the negative terminal on the battery if your wires will reach). Then, using the other probe, begin probing wires/connections/etc. If you find a wire that has shorted to ground it will show a very low resistance (usually a 0 on the display).

WintrSol · Dec 28, 2009

Did you turn the engine so that the points are open? The coil is only a few ohms, like 2 to 6, and will over-current most chargers.

By 'behind the key', do you mean the battery side? If so, my guess would be to unbolt the rectifier and try again.

mitchberry · Dec 30, 2009

wow... honestly i didn't realize people had responded to this thread. for some reason it didn't subscribe me to it...

oops...

sorry....

it's pretty late, but i'll respond in the morning. thanks guys

toehead · Dec 31, 2009

You might have seen this in a different thread, but you can get a rectifier at radioshack that will actually be an upgrade over stock, provided you have an external voltage regulator.

Here's the link.
http://go.motorcycleforum.com/?id=6.../?id=673X1268&url=http://www.radioshack.com/product/index.jsp?productId=2062584

Cool think is, it costs a whopping three dollars

+ 1 on the points idea, especially since you don't have a battery to act as a buffer.

mitchberry · Dec 31, 2009

Have you actually tried that?

toehead · Dec 31, 2009

Yes, it's been on my ts125 for a few weeks now. I mounted it in the stock location and it doesn't even get warm while using it, and the battery charges actually better. My stock was only a half wave rectifier so half of the ac power didn't help charge the bike. This is a full-wave, so all the power gets to the battery.

toehead · Dec 31, 2009

Also mitch, here is a little gem on ebay that might save you some trouble
http://cgi.ebay.com/ebaymotors/suzu...cmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item45ef8213ff#ht_500wt_956

how do you find which wire is grounding?

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