I know very little about vehicle electrics (which will shortly become very apparent). Could it be anything to do with electrical suppression to prevent interference? PJ
Erm "and 2 coils joined in series that (apparently) weren't connected to anything at the stator end" ?
I know what you are saying but that was the whole point of my question. Both my mechanic mate and the auto-electrician that fixes stuff for them were also baffled?
And not all coils are connected to something solid at both ends .. the secondary on a HT coil is *connected* to a gap ;-)
No, that was the point .. the stator end of the cct in question was connected to ... nothing? Well, it was connected to a solder tag on the bobbin but that in turn wasn't connected to anything?
I actually followed the wiring myself ... bike connector .. wire down to stator ... onto coil one .. through coil on to coil two .. through coil two and terminated on tag on the top of the bobbin .. stop / end / finish?
He (and an auto electrician) has even put his DMM over the whole thing and checked for any hidden wiring but nothing. Connect one meter lead to the bike connector end of the cct and you can follow the (~0 ohms) to the first coil and to the end of the second but not to anywhere else? Maybe it *should* be connected to ground and something has melted away but if so why would the other end be connected directly to the +ve battery terminal (and this isn't a 'mod', it's all part of the loom and the same on many bikes)?
Maybe they are there for use on a different model but if that was the case why:
1) Is there a wire (loom) connected to it at the stator end?
2) Is the other end of this single ended cct connected to the (perm, not switched) +Ve battery terminal?
Trust me, I've actually held this assembly in my hand and visually traced all the wires / coils back and can account for every part ... except for this bit?
Em .. not sure how 'obvious' Andy? My first thought were that these were 'spare' to this model but if that was the case wouldn't they just leave them o/c? If that might cause other problems why would you connect one end to +ve battery (not gnd) ?
Well that was the sort of potential answer I was looking for .. maybe something that wasn't 'traditional' or 'obvious' .. ?
I know how stuff changes, things that weren't possible / typical to start with (dimmable low voltage lights etc) but someone comes up with a clever solution and away we go ?
Ok, in this case *I* didn't actually take the stator out myself nor did I measure it but my mechanic mate has been fixing bikes / scooters since the good old days and has been known to rewind an ignition coil or two in his time so isn't easily 'fooled' by much.
So, this particular scooter isn't running, the o/p from the coil that feeds the CDI unit is low and they have changed most things except for this stator. It was whist checking the stator closer he found this weird configuration (with the open ended coil pair) and wondered if this was playing some part in the 'fault'?
In theory it's not *needed* (there are 3 charging coils, 1 CDI ignitor coil and a timing trigger coil / pickup) but if these extra pair were n/a you would have though they would have dealt with them differently (ie, not wiring them into the loom or connecting them to the perm +ve supply)?
And that last bit adds to the mystery .. if they *were* connected to something it would have to be either something like a capacitor (or it would discharge the battery unles the -ve battery supply was chopped with the ignition via relay or summat) ?
The cct diagram shows all the wires going to the places mentioned above (regulator / rectifier, CDI, battery etc) but not a detailed layout for the stator itself (just a generator symbol).
Only time I have seen a coil with only one end connected is when its used as a quick and dirty way to provide an electrostatic shield - typically in a transformer where you wind a layer between primary and sceondary and earth it, to reduce capacitative coupling between tow windings.
Yes. I was thinking that too. Is it possible that the rotor is not actually permanent magnets? In which case you need to run that coil to ground to keep the motor running, and dicoonnect it to stop the engine.
That way the rotor can be simply some lumps of rotating iron. I think.
More good thoughts .. I didn't actually get to see the rotor but I can pop in and look.
To get the above the ('currently' .. excuse the pun) 'unterminated' end of the coil pair would have to be switched to earth to generate the stator field (that could be done by a 'kill switch' or whatever but there were no signs of such a wire? Also if you forgot to use the kill switch it would just flatten the battery with the existing setup (end of the 'unknown use' coils is connected to +ve)?
I suppose if you earthed both ends you would induce large currents in that 'screen' coil and partially defeat the function of the Xformer?
I can't see how this might apply to the stator though (much though I would like it to ) because of the layout ..
Going round the stator you have coils 1,2,3 charging, 4,5 'unknown', 6 CDI feed.
There is a trigger coil that is on a short length of wire tied into the stator (but not electrically connected to the stator .. just passing through) and that just goes up to the ignition / amp / reg unit.
So, 3 'modules ..
Rotor / stator assy . producing charging current, cdi current and ignition timing.
CDI unit, probably powered from the LT supply and 'charged' by the single coil in the stator. (moulded coil looking thing with HT lead sticking out ..)
Ignition / reg module, also powered by the battery (ignition feed) and with the ignition trigger input but also rectifying / regulating the alternator output to the battery (ally heatsink moulded thing)?
Yes, and presumably the engine would run till it had no more fuel.
If it is an 'energised' stator, I'd say that is the logical place to put and ignition switch.
Its often done that way - in the 'earth ' circut, becasue you can then simply have a bit of wire being earthed to chassis to make the whole ignition stuff work, rather than having to carry in a live wire and out again. Well it used to be on older simpler cars anyway.
I'd have to guess pretty low Dave as they look to be about .75mm >1mm dia shelac'd copper wire and probably no more than a couple of hundred turns around a 20mm (ave) dia bobbin (x 2 in series)?
So Pi * d ~= 25m of (say) 1mm dia copper wire for both (if my maths is ok?) .. what's the resistance in that?
I'm going past the shop in a mo so if the stator is still out I'll put his DMM across it and let you know ..
Probably too low a resistance to go straight across 12V without cooking?
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