electrical short on a Znen zn150t-b By southbfd (Read 5,461 times)

[southbfd]

Okay I have a 2008 Znen zn150t-b. It was running fine, then just out of the blue the scooter start blowing the main battery fuse. Every time I turn the key switch to the run position the fuse blows. I have checked the Key switch it is fine I checked continuity on the primary red wire from battery with fuse to chassis ground, Every time I turn on the key switch with the battery disconnected I get continuity tone, when I turn off the key switch the continuity tone stops. I have check the whole harness for shorts or melted and can not find any. I am wondering if it the CDI, Coil, Voltage Regulator or the Starter Silindo. Fun thing is I can hook everything up and disconnect the wire harness going to the dash the and continuity tone goes away. I have gone through and disconnected the different switches on the dash to see I could shut off the continuity tone and find a shorted switch but no such luck. I even checked the light bulbs. I could use any help on the matter, or any troubleshoot tips for different parts.

There are nmo flashers on this bike

[JR]

First of all Welcome to the Forum! Now let me understand you correctly? You get ohms resistance or full continuity on the red wire going to the key switch and touching the chassis (ground)? You are talking about using the ohms scale right?

If this is so then you've got a bad key switch or wires crossed together.

Your key switch should have the following wire colors:

Red = 12Vdc from battery
Black = 12Vdc output from key switch in the on position
Green = ground/negative
black/white or brown/white = kill wire to the CDI

Now here is the test you should do using you VOM on the ohms setting. Unplug the key switch and test it alone;

With the key in the OFF position put one lead on the green wire and the other on the black/white or brown/white, you should get full continuity.

Now with the key still OFF put one lead on the red wire and the other on the green wire, you should get NO continuity, if you do then the switch is bad.

Also lets test the other circuits, put the key in the ON position and do these tests;

Put one lead on the red wire and the other on the black wire, you should get full continuity.

Put one lead on the green wire and the other on the black/white or brown/white, you should get NO continuity.

If all these tests check out correctly then it's time to open her up and lets start tracing wires. Keep us informed we are here to help!

JR

[tvnacman]

You must narrow down the short. Up plug things till the short goes away.

John

[JR]

Well TV if he has the battery unhooked and the meter on the red wire going to the switch has continuity to ground with the key on then the first switch he needs to unplug is the key switch. The red wire ends at the key switch, why go unplug stuff?

If he had said he had continuity on the black wire and ground then I would say move on. But again since he has said red wire then simply unplug the key switch. Test the switch.

If he finds nothing wrong with the switch then it's grounding out through the black wire touching ground a dead givaway and then he needs to move on.

More than likely the black wire has rubbed into the frame and I'm betting right behind the healights.

JR

[tvnacman]

On the doc he said it is commingle from the speedometer area.

Interesting apptoxh Jr , I will keep your suggested method in mind.


John

[JR]

Yes for sure read that and that's why I start at the very "first" switch in the system. Again we know continuity on the red wire with the switch on so if he has the front off then it's easy to unplug one plug to the key switch and check it first.

If it has continuity with the key on from the red to the ground (green) then BINGO we got it but if the switch passes all tests then that tells us that when you turn the key on you will have continuity from the red to the black wire.

The black wire is the feeder or the 12Vdc supply to all of the accessories, horn, turn siganls, brake lights, etc. So again if the red wire has continuity on it with the key on to ground then the ONLY way it could do this is if the BLACK wire is shorted out to ground.

The wires are in a harness and the Chinese are famous for using the little brass crimp connectors to splice wires together especailly the green (ground) wires. They poorly insulate them and over time the movement and vibration can cause these to rub into another wire very easily thus a short.

If the key switch passes all tests then the next step is to take the plug that plugged into the key switch and test for continuity from the black wire to green, betting it has full continuity if so then it's time to start unplugging stuff and tracing wires.

Another famous place that the wires like to rub together is in the brake/tail light area.

JR

[JR]

No Way!

It is normal to have a continuity tone from the red fuse lead to ground with the switch on. It's also normal for the tone to go off with the switch off. The switch connects the red wire to the black wire off of the ignition switch and it grounds through multiple circuits. The fact that the tone stops when you unplug the dash harness is a little bizarre, there should still be enough grounds to have a continuity tone. I'd put a fuse in, unplug the dash harness, and turn on the key. If the fuse blows the problem is not in the dash. You have a security system, my condolences. They are infamous for causing a host of problems. Try the dash test first and let us know what happens. Rich

Read more: scooterdoc.proboards.com/index.cgi?board=150cc&action=display&thread=6403#ixzz1vazYqDiv

The black wire is open until a circuit is completed. The key switch feeds 12Vdc from the fused red wire to the black wire which feeds multiple circuits. The black wire will only give a tone if a circuit is completed say you press the brake handle. If the black wire is shorted to ground such as it's rubbed into the chasis somewhere then it would yeild a tone.

Someone suggested that you would get a tone because of the flasher unit, again not so. The flasher unit gets 12VDc through the black wire and sends it through the gray wire to the turn signal switch and the circuit is not complete to ground until you move the switch for a left or right turn signal.

Also when he unplugs the harness and it goes away, very likely. Most of the harnesses have a huge plug that has multiple circuits that sends current through various places in the scooter. That plug will have the red, black and green wires also so when it's unplugged you are unplugging the circuit that is shorted and have a open circuit on the fused red wire which will not blow the fuse.

Since he said he did the test on the key switch and it tested good, he has a short on the black feed wire to one of the following circuits;

brakes
horn
turn signal flasher
dash light,sideor running lights and/or license plate light "if" it feeds off of the black wire, some scooters do this.

There is one other possibility and it's rare but does happen. The R/R can internally short out and it generally has the red wire tie in behind the fuse which would also short it out.

Simple test for this, unplug the R/R.

Also he mentions having a remote alarm, very unlikely that it is a problem but simple test for that is to unplug it. He will need to check the kill wire circuit and jump it possibly so he can kill the engine.

JR

[southbfd]

Okay If I unplug the Key switch and then test contunity from the red wire from the battery to chassie ground there is no contunity. But If I put the key switch back in line and turn it to the run position I get contunity to chassie ground. But if I unplug the dash harness just the big connector not the little ones Contunity stops.

Keep in mind I have the security systems as well. The wiring on the key switch is red, green , black, black/white. On the connector it is red, green, black and pink, which goes to the securtiy system I think.

When I get off Work I will unplug all devices from the harenss. What is the R/R

[JR]

Regulator/Rectifier. This converts AC to DC and then regulates the output. You should have four wires on it but it could be five?

Also the plug that plugs into the Key switch with the red, black, green and pink, I'm betting the pink goes to the CDI. It als may change color at another plug and go back to the black/white you mentioned on the key switch, the Chinese are famous for that too. LOL

On that plug take your VOM meter and do a continuity test on the black and green wire, if you get tone then we know the black wire is shorted in the circuit somewhere?

On the security system? You are refering to what we call the remote alarm? In other words you mhave a little remote hand held elctronic remote that you can set the alarm with and if the scooter is touched or bothered it will sound off and the lights will flash?

If it is like all other alarm systems it does NOT feed off of the key switch but rather a direct tie in on the red fused wire from the battery. It has to have power at all times to work and would not if it came off of the key switch. It should just be a little box with a big plug of lots of wires going to it with a alarm horn by it. It's easy to plug and unplug.

We'll be waiting for your results when you get off work.

JR

[southbfd]

Okay here is the latest.

I plugged everything back in and reconnected the battery but unplugged the main dash harness and turn on the key swtich. The fuse did not blow. So I am guessing it must be in the dash I guess. Or could it still be the DC CDI. I hope we are getting closer.

My R/R has six wires coming out of it just for information.

[alleyoop]

To Verify if the CDI is a DC CDI check the red wire if has 12V it is a DC CDI if it doesn't then its a AC CDI.
Alleyoop

[JR]

Alley Scott has sent me the wiring diagram from his manual and we will be on the phone about this problem. If this diagram is correct then we have a different animal all together. Znen is tough to find info on so when I verify some things with Scott we'll sink our teeth into it then.

JR

[alleyoop]

COOL!! Another Hard to get manual in your hands and will be in your SCOOT PDF FILES.
Alleyoop

[southbfd]

Here is what I know so far

1. With key off and the contiunity test hooked to the black wire at the key switch & chassie (ground). CT meter read .744 with key switch on meter reads OL

2. With all connectors unplugged execpt for the dash harness the fuse blows.

3. With all the connectors unplugged and the dash harness unplugged, Key switch on fuse does not blow.

4. With all the connectors connected including the dash harness and the key switch on the fuse blows

5. With dash harness unplugged and the CT meter hooked to the chassie ground and the B/W pink with at the key switch harness and key off Tone on CT meter.

6. With all connectors connect3ed including the dash harness and the Key switch off the the fuse does not blow.

7. With the dash unplugged and CT meter hooked to the chassie ground and B/W pink wire at key switch and key switch on, No tone on the CT meter.

8. With all connectores plugged in execpt the dash harness now the CT meter hooked to the green wire at the switch and chassie ground. Tone on the Ct meter with the key in the On or Off position.

9. Switch Test

Key off- B/W wire and Green Wire --- Tone
Key on - Red wire and Black Wire --- Tone

10 . Witrh CT meter hooked to the B/W pink wire at switch connector & chassie ground, with all connectors unplugged expect for key switch. Tone on CT with Key in the off position and No Tone with the Key in the On position

Everything was done the battery hooked up.

So I am guess I have a short in the Dash Hanress

[JR]

You are narrowing it down and I sent you a email, my thought is the diagram you sent is generic and not your scooter? the Chinese do that crap! We'll talk and go from there.

JR