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[Adrian]

Oh dear, it sounds like your bike's electrics are a bit of a disaster.

What I'm thinking is that someone purchased and fitted the later 4 wire stator without realising what had changed when the later AC headlight system was introduced.

Please will you check and see what type of handlebar controls you have, the Magura or the later Minda type? This is a clue, but it also matters in terms of headlight wiring.

Remember this. The 4 wire alternator runs in two electrically isolated halves. With the yellow wire unconnected and the orange wire grounded ONLY ONE HALF OF YOUR ALTERNATOR HAS BEEN CONNECTED, via the red and black leads to the Powerbox in your case. That means that with the headlights on, the operating half of your alternator is being overloaded, while the three coils that SHOULD be powering the headlamp separately are doing nothing!!!

The yellow wire is the supply to the headlamp and the main beam warning light, NOTHING ELSE. It feeds the headlight via a separate AC regulator. The orange wire is the return wire from the headlamp directly to the alternator, IT DOES NOT GO TO EARTH (the Minda switchgear is designed for this, the Magura isn't). Think of a modern domestic AC electrical appliance. It may have a three pin plug, but on many appliances with decent insulation, the earth pin on the plug is now just a plastic dummy. There are only two wires needed, brown (live) and blue (neutral). So comparing AC headlights with domestic appliances, the 12V yellow wire does the same job the 230V brown wire, and the 12V orange wire does the same job as the 230V blue wire.

If you don't have the correct switchgear or the AC regulator, then the Snidal conversion for the 4 wire alternator is the only way you will get it to work fully. This means ALL FOUR leads will need connecting to the AC side of the Powerbox, EITHER the red+orange alternator wires on one side and the black and yellow on the other, or the red+yellow on one side and black and orange on the other. Read and follow his instructions TO THE LETTER.

It would be very tempting to give up on the 4 wire alternator, buy a Lucas RM21 with just two wires and simply hook them up to the AC side of your Powerbox. Job done.

Phew!

A.

[Brazilla]

Hanks again Adrian, having read historic posts on the subject it seems like you are the electrical guru par excellence around here



It seems my bike was a bit of an anomaly when I got it, supposedly a 97 but with the four wire red/black alternator and minda switchgear. I was told it had only about 100 miles on the clock because the original owner had passed away shortly after getting it and it had become an ornament in a pub! Seems odd if the alt and switch gear had been upgraded right off the bat. Maybe the tale and the mileage is untrue, anyway I put 4k miles on it since I had it. Is there a place I can check year by vn number? Bike has served me well, Regulator failed a while back which was when I fitted the powerbox and it has run fine since, gradually phased out the Minda stuff as well which had been fine until this lighting failure, now I'm in for the full overhaul though. Seemed like a good idea at the start haha but I'll be walking to work on Tuesday!




Before I took all the loom apart I made some notes on where stuff was connected to, the orange lead from the alt was connected to about a half a dozen other earth leads coming from front and back, this was buried in the loom and they were all help together by a bent metal clamp, looked pretty dicey! It wasn't connected solely to the earth from the headlight which is where I think you say it should have been.




So, having junked all the existing loom I'm in the position of wanting to start from scratch, I think I might try redraw legibly and upload a circuit diagram later to show what I'm attempting, but in a nutshell it's alternator (now wired so all coils feed into powerbox, thanks for that) simple charging circuit via the ammeter, linked ground points behind battery and in headlight shell. Iof course coil, points and brake lights. For switchgear I'll be using that chromed indicator switch and the horn/dip. Yesterday I was using a generic 12v 25a toggle switch as both lights and ignition (I plan on going keyless but putting a secret disable switch somewhere) it'll be a much simpler circuit than what was originally fitted, I think I am right in saying that a shorter circuit means less resistance so higher ampage which is why I melted a few wires yesterday (I've now fitted 17amp wires in some places and 27amp connecting directly to the battery) I think they also melted as I was impatient and foolishly tested a circuit that had no load and therefore the amps exceeded the rating of the wires. I may have completely misunderstood he nature of amps and resistance here, GCSE science was a while ago and as you may have guessed I am a bit of a novice who likes to bite off more than he can chew!

[Adrian]

You're Elcome!



Going all DC is fine if your alternator is phased correctly, as per Snidal, and you want a simpler wiring loom.



I'm no guru, but I like to give my electrics a fighting chance. I have never been bothered about resistance, but I do try and make sure my wiring has a high enough rating plus a little more to cope with the what's being asked of it. If Watts = Volts x Amps, Amps = Watts/Volts. Thus a headlamp main beam wire for a 60W bulb on a 12V system will have to carry a 5A current, so I like to use 8A rated cable at that point in the loom.



I can't see how simply using a 25A rated switch on its own can melt wires, UNLESS you are creating a short circuit somewhere, eg postive to negative without a bulb in circuit - is THAT what you mean when you say you foolishly tested a circuit that had no load?



My understanding is that these switches are rated UP TO 25A. You can work out whether that switch is man enough by working out the current that will be drawn by each part of the system, then add them all together for when you're braking while using the indicators with the headlight on! If it's still less than 25A total the switch is OK. Just put appropriate fuses where needed.



You can reduce the power required by converting as many lights as possible to LED, in fact you can get nice bright LED H4 headlamp bulbs that only draw about 2 amps.



While all of my bikes on the road have fully rectified systems I am looking to put together a lean-burn Bullet engine with an AC headlight alternator, but this will be a SIX wire alternator with CDI ignition, three separate systems powered by one alternator...



A.

[Brazilla]

Sounds interesting. Yes I think I must have had a short circuit somewhere which caused the melting wires/switches. Wherever it was it's now gone, I have all the lighting tested and sorted and ready to patch in but I want to get ignition and charging working before I add that in. I tried to start yesterday with no success and no spark when I lifted plug out, I am going to double check I get voltage to all the right places but I am now worried the heat from the short killed either the coil or the powerbox, does anyone know a multimeter method for checking functionality of these two bits? I was going to check points using a light bulb? If they're buggered it might be a good time to upgrade to the Boyer mk4. I figure getting a real good spark and charging circuit before I add in the lights is a good way to go.

[Brazilla]

Found an old forum post with resistance values so I can check coil, will then rig up a simple circuit to check spark. Just need to know a check for powerbox now. Once I have done all this and have everything working I will upload a circuit diagram which may be of use to others in the future who want simplest possible wiring harness!

[Brazilla]

Tests complete and here's what I found:

[Adrian]

I did manage to kill a Powerbox once, but there wasn't much uncertainty about it. The internal capacitor exploded, showering the back of the bike with the now ex-capacitor's stuffing and blowing a dent in the top cover of a the l/h rear shock absorber.



If you have killed your Powerbox, the Sparx SPX023 reg/rectifier has a capacitor and is quite a bit cheaper. One of these will at least be used to let you know if your alternator is still working.



Heaven forbid, but if you have killed the more than a few wires, it at least gives you good reason to bin the lot and go with all new. Ouch. £££.



A.

[Brazilla]

Well, I tried but could not get anything from the points, I said that once they failed I would go EI so this is that time, still confused why they broke but hey!. So it's a new coil and EI for me tomorrow, will hope powerbox is ok for now, can at least test spark with and without it to determine if it's a problem. I once had a capacitor explode in a guitar amp I owned, quite a sight! For testing spark I read you can do output from points/EI to + on coil then - on coil to frame, think I remembered that right and not sure how battery fits in! Anyway, thanks for your help I'll let you know how I get on!

[Brazilla]

Right I have the engine running again, need to confirm alternator is working as my cursory dmm test didn't tell me it was, hoping that's not fried too!

[Brazilla]

Tidied up and finished off wiring today but pretty sure alternator is lunched...increased throttle made no difference to any of these readings.
Reading across battery with engine running was under 12, AC reading from alternator was 6.5. Reading from Red and Black leads out of powerbox showed nothing on DC but oddly seemed to show a reading on AC... must investigate further.

Could someone confirm a ballpark for the reading I should expect from all coils of 4 wire alternator combined? What should I expect from the DC outputs of the Powerbox...guessing about 13.5v?