Suzuki Sepia ZZ, voltage out of control!

[TygerTung]

I have a Suzuki Sepia ZZ it is probably about a 94 I'd imagine.

I fitted up a new good second hand piston and barrel, and that runs fine.

Unfortunatly now the voltage doesn't seem to be regulating at all, if you increase the revs pretty much at all above idle, the headlight and brake light blows instantly.

I have tried two other voltage regulators, but this has no effect.

What could cause this? It has me stumped.

Cheers,

Sam
______

[notme]

If it has a conventional charging system, step 3 of this thread will tell you what the problem is.

http://www.kiwibiker.co.nz/forums/sh...shooting-steps

Could be as simple as a stuffed battery if you have already replaced the regulator with a known good one.

Are any alternator parts involved in the engine bits you changed?

[TygerTung]

Well yes, the battery is rather flat, maybe this is the cause. It doesn't usually do this with a flat battery, but who knows?

I put the battery on charge before I went to play in the brass band at the New Brighton ANZAC day service. Will go and check it out now.

No, I didn't change any alternator parts, just the barrel and piston.

Thanks for the link to the troubleshooting page, I probably should have checked that first. I'll go through all the trouble shooting steps and see if I can work it out.

[notme]

I spent a few seconds on google finding out that this is a scootah not a bike, so the advice for the charging system doesn't apply fully.

How sure are you that the two other regulators were good? Unlikely that they are both faulty, but then again it's the most obvious cause of the symptoms you have.

What does the battery voltage do with revs? I would think that the regulator units should either work properly and keep the lighting voltage within limits as well as the charging voltage, or the regulator would be completely stuffed.

So if the lighting half is buggered the charging half probably is too....

[TygerTung]

The battery voltage goes quite high with revs, around 17 volts at high revs.

I believe it may be putting out AC however, as the voltage reading is much higher on AC.

I put an oscilloscope across the headlight terminals and this is the wave form at idle.

At higher RPM the waveform goes huge and bezerk, however I cannot take a photo of it doing this as I need to hold the camera.

[hayd3n]

so bacisly is giving to much current
is it a 6v or 12v system

[notme]

The battery voltage goes quite high with revs, around 17 volts at high revs.

I believe it may be putting out AC however, as the voltage reading is much higher on AC.

I put an oscilloscope across the headlight terminals and this is the wave form at idle.

At higher RPM the waveform goes huge and bezerk, however I cannot take a photo of it doing this as I need to hold the camera.

There shouldn't be AC at the battery...if there is, there is something really screwy (and bad) going on!

There also shouldn't be anywhere near 17VDC at the battery - that means the regulator is not working as it should.

The head and tail lights are usually on AC so that's all fine, but the voltage is not being clamped at 12V AC like it should, and so the bulbs are blowing. The regulator should be performing this voltage limit function, i.e. keeping the lighting on about 12VAC and the battery charging on around 14VDC.

So the regulator is the most likely culprit - where were the ones you tried from? brand new? known good? Workshop floor? Can you borrow one from a mate or similar?

[TygerTung]

One was out of a box of spare parts, one was out of my old scooter which stopped due to the base gasket blowing out between the cylinder and the crankcase.

The AC was measured on the lights, I didn't realise that the lighting circuit was AC. It definitely is AC, as I hooked it up to a speaker and it was outputting a sound directly related to engine revs (makes sense I guess). Have to cook some lasagne for my sister in laws birthday party now, so will check the battery waveform after that I guess.

I might have another regulator sitting in a box of bits perhaps, I'll check there and have a look.

Could it be a case of a couple of wires are shorting doing this? It was fine before I pulled it apart.

I think there is well over 30V+ AC at the headlight.

[notme]

One was out of a box of spare parts, one was out of my old scooter which stopped due to the base gasket blowing out between the cylinder and the crankcase.

The AC was measured on the lights, I didn't realise that the lighting circuit was AC. It definitely is AC, as I hooked it up to a speaker and it was outputting a sound directly related to engine revs (makes sense I guess). Have to cook some lasagne for my sister in laws birthday party now, so will check the battery waveform after that I guess.

I might have another regulator sitting in a box of bits perhaps, I'll check there and have a look.

Could it be a case of a couple of wires are shorting doing this? It was fine before I pulled it apart.

I think there is well over 30V+ AC at the headlight.

30V on a 12V headlight = really bright then poof, blown headlight..... so no wonder they are dying!

If it worked fine before you took it apart and it doesn't now, it must either be some shite murphy's law coincidence, or maybe there are some wires that could be damaged to cause this effect. I can't think how that would happen though - the regulator should be all self contained.

[TygerTung]

I measured the voltage across the battery, it isn't the cleanest, but I guess you would expect that, it doesn't really need to be I guess as it is just powering some indicators and horns etc.



When I removed the battery the wave form was pretty flat with small humps.



I am pretty sure it is DC, but I am not experienced enough with an oscilloscope to tell.

[notme]

I measured the voltage across the battery, it isn't the cleanest, but I guess you would expect that, it doesn't really need to be I guess as it is just powering some indicators and horns etc.



When I removed the battery the wave form was pretty flat with small humps.



I am pretty sure it is DC, but I am not experienced enough with an oscilloscope to tell.

That all looks fine (would be nice to be able to see the screen scaling though!)

It's DC-enough, and it proves the regulator is at least taking care of charging the battery. Why the regulator is not regulating the headlight voltage though I have no idea...

You can always double check by using your digtial multimeter and switching it to AC volts and DC volts while connected to whatever you are measuring the voltage across (headlight, battery etc). For any given voltage you will read AC and DC volts, but one will be much bigger. That's the dominant voltage....

For example in your case you will read say 13V DC across your battery - if you switch to AC you might see 1/2 a volt or 1 V. so Your battery is seeing 13V DC with a small AC ripple, simply because it's not perfectly flat DC as you have already noticed on the scope. If you did the same experiment on your headlight, you would read (ideally) around 12V AC with a small DC voltage because the AC waveform is not completely balanced. Crystal? :-)

Anyway I still suspect your regulator....there's no way it should let 30VAC through to the headlight. Also note that I am hoping there's not some other black box you have forgotten to mention, and that your scoot doesn't have some weird arrangement of a seperate regulator for the lights which is hidden under the seat or something.....

[TygerTung]

I don't think the lighting circuit is regulated, as it continues to illuminate even if the regulator is removed. Maybe a plug was inadvertantly installed 180 degrees out. I have removed the stator, and it looks fine, I checked it against another good one and it gave the same readings. I'll re-install it tommorow and try again. I think the output plug may have been around the wrong way.

[TygerTung]

It turns out that the plug going out of the alternator was misaligned, feeding electricity into only 1 of the two wires and the wire which was getting electricity was the wrong one. Also this cooked the regulator, so I had to go and get another one. All sorted now though.