Skip to main content
000000 000003 000006 000009 000012 000015 000018 000021 000024 000027 000030 000033 000036 000039 000042 000045 000048 000051 000054 000057 000060 000063 000066 000069 000072 000075 000078 000081 000084 000087 000090 000093 000096 000099 000102 000105 000108 000111 000114 000117 000120 000123 000126 000129 000132 000135 000138 000141 000144 000147 000150 000153 000156 000159 000162 000165 000168 000171 000174 000177 000180 000183 000186 000189 000192 000195 000198 000201 000204 000207 000210 000213 000216 000219 000222 000225 000228 000231 000234 000237 000240 000243 000246 000249 000252 000255 000258 000261 000264 000267 000270 000273 000276 000279 000282 000285 000288 000291 000294 000297 000300 000303 000306 000309 000312 000318 000321 000324 000327 000330 000333 000336 000339 000342 000345 000348 000351 000354 000357 000360 000363 000366 000369 000372 000375 000378 000381 000384 000387 000390 000393 000396 000399 000402 000405 000408 000411 000414 000417 000420 000423 000426 000429 000432 000435 000438 000441 000444 000447 000450 000453 000456 000459 000462 000465 000468 000471 000474 000477 000480 000483 000486 000489 000492 000495 000498 000501 000504 000507 000510 000513 000516 000519 000522 000525 000528 000531 000534 000537 000540 000543 000546 000549 000552 000555 000558 000561 000564 000567 000570 000573 000576 000579 000582 000585 000588 000591 000594 000597 000600 000603 000606 000609 000612 000615 000618 000621 000624 000627 000630 000633 000636 000639 000642 000645 000648 000651 000654 000657 000660 000663 000666 000669 000672 000675 000678 000681 000684 000687 000690 000693 000696 000699 000702 000705 000708 000711 000714 000717 000720 000723 000726 000729 000732 000735 000738 000741 000744 000747 000750 000753 000756 000759 000762 000765 000768 000771 000774 000777 000780 000783 000786 000789 000792 000795 000798 000801 000804 000807 000810 000813 000816 000819 000822 000825 000828 000831 000834 000837 000840 000843 000846 000849 000852 000855 000858 000861 000864 000867 000870 000873 000876 000879 000882
English French German Italian Spanish

6 Volt or 12 Volt?

Forums

My 1959 '99' is 6V and I intend using it mainly in the daytime so I've restored it as per original with a new PRS 8 switch and alternator stator and rotor.  Is it worth me upgrading to 12V, considering that I'll be using low current LED lights?  I also have NOS 6 Volt Fiamma windtone horns in black instead of the usual red - not that easy to find!

Permalink

hello now 12 volt is a lot better  with a PRS8 you will need a 12 volt  alternator with lighting and Ignition coils  .your anna  j  

Permalink

I have never had a Brit bike with an alternator, but my understanding is that even the earliest Lucas alternators (they have a smaller OD on the magnet, ID on the coil) will easily convert to 12V with a suitable regulator

Paul

Permalink

Al, our electrical guru , has stated oft times that you do not need a new alternator to run 12v electrics. If you have an early 3 wire one connect 2 of tham together. Worth a serch through back copies of Roadholder on line. Worked for me, I used a PODTRONIC regulator. Probably you have distributor ignition, in which case Lucas recommended that the internally mounted distributor capacitor is diched and replaced with a 12v rated one which can be externally mounted.

In reply to by anna_jeannette_dixon

Permalink

Thanks Anna but that doesn't really help.  I don't need much more lighting power, especially as I am going LED, which are brighter and consume less, and I don't intend to do much, if any, night riding.  (All my lights at home are LED now.)  Changing the new alternator isn't an option either. I'd need several good reasons to change. Are there many?

Permalink

Sorry, I didn't make myself clear with my question.  It's not what I need to do to change to 12V, it's what are the great advantages that might justify the expense?

Permalink

Hi Lionel,

6V is perfectly ok if you are not intending to ride in the dark, and if your LED headlight is good then nighttime riding is probably ok as well.

Just make sure all connections are good and tight and stick with 6V, no point in spending money changing to 12V.

If you intended to change to electronic ignition, then that would be a different matter.

Tony

Permalink

Even if you stick with 6 volts, it is probably worth fitting a modern regulator - Al Osborne sells one for 6 volts - it should prevent the battery from frying or flattening.  The old Lucas switch system introduced an extra alternator coil to up the output when the lights were used, and you won't need the extra wattage if you have LED lamps.  As Charles suggests above, except for sticking with 6 volts if you feel you must.  But if you are to add a modern regulator anyway, the only reason to stick with 6 volts (since you have an alternator) is to save buying new bulbs and battery.  (Perfectly sound reasons...)

Permalink

It would be worth checking whether automotive LED lamps will operate at 6v. I would have thought that they would need 12v to switch on. LEDs have a switching voltage which will normally be set for 12 volt usage as that is what most of the customers need.

If you have LED headlamps working at 6v already please let me know. 

Good luck.

Permalink

Supplied by Paul Goff, it works on both 6v and 12v, positive or negative earth. One lamp does all that, no need to specify the bike voltage or earth polarity. I am not sure if fittings other than BPF are available yet. It is bright but have not yet ridden with it in the dark. BPF beam pattern was always poor so unlikely to be any worse.

Ian McD

Permalink

Yes, the BPF beam pattern is poor.  I recently fitted a halogen bulb, and it's still a poor headlamp, but a bit brighter.  Riding at night on roads without overhead lights or cateyes is scary, if there is no car / lorry ahead.  Construction and User regulations may apply.....

I have not tried LED bulb replacements, but hear that the beam pattern is poor. 

Paul

Permalink

Several points of miss information here. You don't need a '12V' stator the RM19 or earlier will 'hold' 12V if needed. LED are in fact 2.6V or there about. The people who 'make' them into a case/bulb etc for use on vehicles can make then Negative earth, Positive earth 6V or 12V as the market choses. It just so happens that the Negative earth 12V brigade-market is the greater, but as is said above Paul Goff is supplieing a multi voltage/polarity item.

6V-12V, yes there is losses with 6V and old wiring, but one of the biggest areas of concern not mentioned above is battery charging. The old 6V system with regulation of the battery charging done by the PRS8 doing its thing, was reliant on a largish 6V lead acid battery venting a bit of electrolyte from time to time if it got a bit hot under the collar-fine for 1959. IF you use a Burlen sealed battery on this system you will cook it. If you use a 4AHR sealed alarm battery (as is becoming very popular) you will cook that too. 12V will allow proper charge control and a better choice of battery and lamps. You can also look at my web site via the orange Icon and find out more. I even have a loom kit specifically for 6V

Permalink

Besides better output control, going 12V will give a far greater choice of bulbs, whether tungsten, halogen or LED. 

If you are using a pair of Cyclons, you can rewire them in series instead of parallel to make a 6V pairing into 12V.

Paul

Permalink

I had this debate sometime ago with myself as the bike concerned was 6 volt and very much original. In the end went for an upgrade to 12v as the lights were so much brighter and more importantly you could actually hear the horn. It was thus a safety factor. It paid off when someone nearly ran into me as he heard the horn. I am not sure with the pathetic note before it would have done any good. If I flash the headlight it is also brighter. I only use the bike normally in day light hours to toddle around quiet lanes but when caught out late one evening the 12v beam on a standard bulb helped with night vision and I presume others could see me easier than the 6 volt candle I had. Anyway trust this helps. Cheers Hugh   

Permalink

When you fit a 12V headlamp we usually go to 45W that is 4A if we fitted the same wattage at 6V it would be 8A, the original wiring had a limit of 8A when new but with 'original' wiring, all those bad connectors etc and the higher current, even the same voltage drop say 1V at 6V is 16% while 1V at 12V the loss is 8% so yes you lose a lot less at 12V. BUT 6V can be made as good/bright, as a 45W head lamp is a 45W headlamp whether it is 6V or 12V assuming you take care of the cable/connection losses. If you can't be bothered about rewiring the bike 'properly' for 6V and sourcing a 45W-6V lamp then go 12V.

Permalink

Before LED's I would have always recommended converting to 12V, but the actual voltage LED's run internally is 5V then that no longer is the issue. So that leaves you with voltage regulation, fit a 6V regulator, rewire so the alternator is at full output all the time, fit LED's that take 6V and you are  good to go. The LED main bulbs I fit to my 12V bikes all say 5V to 30V, its the smaller ones that you need more care on picking.

Permalink

Thanks for the response chaps.  My main point was debating whether it is really worth the extra expense of changing my kit to go with 12V, as I don't expect to do much night riding. I have bought what I believe are quite rare 6V Fiamma "windtone", horns in black not red!  The first time around (1964 - 1971) I had a pair of cheaper versions mounted on my Britax Double "D" front crash bars.  Although I stupidly scrapped those many years ago because the were rusty (!!!) I bought another pair (two pairs actually, but I will be selling one) plus a pair of Britax rears with fittings.  I will mount the horns on these - QD for any Concours showings.  They are loud!  I will also mount a Bren gun on the bars for anyone who doesn't hear the horn!  I think the twin Fiammas will be at least as loud as whatever 12V horn is acceptable on a 1959 bike. 

LEDs are definitely the way to go and I've fitted out my home and motorhome with them.  My reasoning is that I coped extremely well with 6V systems in the darkest lanes of the South West of England so I should be OK with the brighter and lower amperage LEDs,  My Dad was an Auto-electrician as well as a domestic one, so I learnt a lot about electrickery from him from about the age of 5! (68 years ago) I'm nor sure about fitting a 6V regulator to my 1959 model.  I assumed I would still use a rectifier system and probably the new PRS8 switch could still be wired as normal?

Tanks AL, I will be very attentive to cabling and losses and the use of a voltmeter and ammeter will be important.  I prefer to tin my cables and solder brass nipples using a low wattage soldering iron - as my Dad always recommend.  A 100 watt kit is no good for copper cables IMHO.  It can cause brittleness when overcooked.

Permalink

If you can solve the two main issues with 6v  then there is no reason to uprate to 12v. Led's  have not had a good press with beam projection but progress is being made.  Charging regulation is a bit haphazard with the psr8 switching and as AL has said a biggish lead acid battery will provide a crude buffer.  The  other issue could be when your 3 wire old alternator dies and you have to buy a new more powerfull 2 wire replacement. Charge control will need a re-think. New PSR8 switches may not be as good(!!) as the orriginals I still have an old one in use. With care and a crafty bit of fine fishing line to hold the springs the psr8 can be cleaned and rebuilt.

Permalink

Yes this switch is quite amazing considering how old they are-designed in the early 1950s. The rebuilt switches from Far East are not always up to scratch, and when rebuilding (which is straight forward) 1/4 inch becomes 6mm........so swapping parts can become a problem. (see my web site).

It was reported in the Motorcycle Press a while back that the PRS8 was over complicated. I very much doubt if Lucas mad a switch that more complicated than it needed to be, certainly there is several functions within the PRS8 that need some understand and not always needed, but I think Lucas did really know what they doing in the early 50s. I would like some further info re Lucas 1950s-see fresh Post.

Now another piece of 'not quite right' info above-you do not have to buy a 2 wire alternator, the 3 wire RM19 is still available, so you can retain 6V if you want. But you still have to have a74mm rotor.

LEDs are 2.6V ish, if they are made into a lamp housing and they say 5v that is because they have a 5v regulator installed. Which is a very good idea, as LEDs (the raw electronic form) very easily suffer from over current caused by over voltage which does not really cause them to be any brighter. So they can burn out very soon if you over volt them. Cheap ones on my car-said to be 12V soon failed as of course the car runs at just over 14V (14% increase).

Hugh above had a bad horn-blamed on 6V. Not so, a crap horn is a crap horn. You can have one on 6V or 12V. And a decent one on 6V.

Permalink

My 6v  original  horn from 1960 has been running on 12v for the last 20+ years , and very loud it is too.  Not  exactly a recommendation  but what is there to loose?.

Permalink

It's always good to have inputs from other people - whether you follow them or not, so I am very grateful for the opinions given.

My conclusion is that it isn't worth the bother to change from my original 6V as a) I will be using LED lighting throughout, b) I managed in the 1960s with 6V lighting but my LEDs will be brighter , c) my new 6V Fiamma windtones will be much louder than a Lucas Altette (actually a restored HF1441 correct for my bike) of either voltage and d) at my age (73.5) I am unlikely to do much night-riding anyway!

Take care out there!

Permalink

FIAMM horns of course.  Italian made and very loud.  I bought the complete boxed pair new-old-stock. It comes with a relay an is black and chrome rather than red/chrome, like a pair that's on eBay right now for £59.95. (https://www.ebay.co.uk/itm/FIAMM-Classic-Bikes-Cars-ElectroMagnetic-Horns-CTP-Super-6V-Hz-510-410/333152583195?epid=15019633476&hash=item4d9170fe1b:g:JXUAAOSw9NhbAUdi) I bought mine a few years ago for around £40, or maybe less.

Permalink

Being not a technical person I changed to 12 v and got brighter lights but an earlier post replying  suggested this may not have been needed being achievable with 6v and newer bulbs.  I only ride really in daylight so the lights were a byproduct (the flash is more visible) but felt really needed a louder horn in today's world. This did prove effective in a potential situation where the horn alerted the car driver to my presence - he not having seen me despite high vis jacket.  I didn't know if this was possible with a 6 volt system at the time not having heard of Fiamm horns. Certainly my replacement horn was cheaper than £60. As I recall I simply combined 2 of the 3 wires from the alternator and changed the rectifier for a combined rectifier/regulator but it was a long time ago. Regards Hugh

In reply to by hugh_coombs

Permalink

I used to have a pair of these horns back in the 60s, as I said, and they were loud.  Cars up to the 1950s were 6 Volt.  I'm not sure what horn(s) you had that you found to be very loud.  Not the original Lucas I suspect?  As I also said in my earlier post - a mounted machine gun is another way of warning errant motorists! LOL!

Permalink

To uprate to 12v you only really need a 12v battery and one of Al's A Reg 1 rectifier/regulators and some bulbs. So much better than the dodgy Lucas switching coils in and out setup.

I don't rate LED headlight bulbs. A shockingly useless not to say dangerous beam pattern. A standard BPF is much better. Also, what's the point of generating 100 watts or so and not using them? Might as well put them through the headlight which had the added effect of keeping the reflector and headlight shell warm and dry. Similarly instrument lights - I like my chronometrics to have a little heat source to help keep them dry.

I do use LED stop/tail bulbs though. 

 

Norton Owners Club Website by White-Hot Design

Privacy Policy