I have been looking through the posts from 2006/07 on converting to 12 volts. Barry Riseley and Malcolm Watts led the threads. I'd be grateful for some definitive guidance on using the standard 6 volt dynamo when converting to 12 volt coil/regulator/battery as I can't find the results of Barry's proposed experiment to see what long term effect this would have on the dynamo - but I do note that Malcolm has successfully run such a set up for several thousand miles. Being a thickie when it comes to electricity can someone give me an idiot's guide to what to do and also tell me what output I should set up via the third brush? Sorry if I am re-opening a well worn thread but guidance would be much appreciated. Nick

Hi Nick,

If your car is running OK at 6v then don't make any changes to the dynamo settings, simply change your battery to 12v, change your bulbs and coil to 12v, add a resistor in series to the fuel gauge and wiper motor( 33 ohm 1/4watt for fuel gauge, approx 2 ohm 100watt to the wiper ) and you will have a 12v system.

You can change the wiper motor to a 12v version if you want. If you don't have an electric wiper or a fuel gauge on your car then the conversion is easier.

Just to put your mind at rest about the dynamo; the faster the dynamo turns the more volts it produces therefore most of the time, whilst you are driving, the dynamo is producing more than 6v, indeed more than 12v, sometimes up to 40v !!. The battery is the voltage control on an Austin Seven. You will find, however that the ignition warning light will take longer to go out as the engine has to be turning approximately twice as fast as a 6v version before the 12v battery starts to charge. This will not be a problem unless you spend all your motoring life on the M25 and you are either crawling along at 10 MPH or waiting in a queue with the engine ticking over. Having said that the average 12v battery has a greater Ampere Hour rating than the typical 6v battery and will keep your engine running, even with a discharge, for longer.

Once you have the system running you will find you can reduce the current ( amps ) output from the dynamo as 12v uses half the amperage of a 6v system if you are using the same wattage bulbs etc. You do this by moving the third brush in an clockwise directionh when looking at the distributor end of the dynamo. Mine runs at 6Amps on summer charge and 10 Amps on winter charge.

This has the additional benefit of the dynamo running cooler. Don't be misled into thinking that 12v puts more load on the dynamo, it is the opposite !

If you want to chat about it email me.

Malcolm

Malcolm,

this is interesting, I had always heard that 12v conversion involved boxes of (unreliable) electronics and removing 3rd brushes, what you tel seems to dispell this...

What about the voltage regulator, does this have to changed to 12v or will the 6v still work?

Interested of Bearsden..

Thanks Malcolm, that is hugely helpful. I would only echo Ruairidh's question about the voltage regulator - use the 6v or change to 12v, and if it does involve a change can you recommend which model of regulator is best to use? I presume that if a change is needed the wiring to the ignition/charging rate switch is still straightforward?

Nick

Hi Both,

Sorry, I forgot the 'regulator' or to give it a more accurate name, the 'cut-out', there is no regulation.

I have used 12v versions of the same cut-outs that were originally provided on my 2 A7's, 1929 RK saloon and 1934 RP saloon.

Some people are using a 33 ohm resistor in series with the cut-out to reduce the voltage across the coil of the cut-out to 6v on a 12v system. You will need to isolate the 'E' terminal on the cutout by cutting the wire within the cutout which links to the 'E' terminal and replace this wire with a 33 ohm resistor. Please Note. The wire which needs to be cut is part of the cutout not the car wiring loom that goes to the 'E' terminal.

I use the 12v replacement cut-out because it is simple and they are relatively easy to find at the larger autojumbles for about the same money as the 6v version. If you are quick about it you may well be able to buy a 12v version and re-coup your money by selling the 6v version !!

I have been a 12v A7 man since 2000 and although I have had the odd broken wire inside the dynamo ( and who hasn't ? ) I have had no problems, only benefits. At the moment the total A7 milage per year between our two cars is 7000 miles p.a. and has been for at least the last two years.

Would support what Malcolm says. I've run this system, but with the third brush backed off to its minimum setting, with no problems at all. For cut outs, you can use the 12v Austin 10 version or use a more modern RB106 Lucas type regulator/cut out that are available, repro, new, for under £20 and just wire in the cut out.

I now have a fully re-built, 12v 2 brush dynamo that is the ultimate solution but managed fine for two years on 12v without it.

STEVE

Nick

to sumarise there are "different" ways of doing it as you seem to be aware!!
I prefer Malcolms approach, but there are different ways.

Malcolms basic approach with a 12V cut out is nice and simple and straightforward and I prefer that personally.
You can also use an electro mechanical regulator to act as cut out and to regulate charge slightly better, although there are issues with this, which have been covered before in previous posts.
You can also use an electronic "solid state" conversion, which is available from some A7 suppliers. This device controls the charge rate and also act as cut out. It does a very good job of controlling the charge, much better than any other method in my opinion, BUT BUT they are reputed to be very fragile and unreliable due to there electronics content!

Or you can be awkward and do what I did! I removed the solid state conversion I had that was working fine , and then used a rheostat in between the f and D terminals as per the standard high/low charge resistor to regulate the charge manually from a dashboard control. I used a Schottky diode to act as a very cheap cut out (£1.71 from Maplins, so I carry a cheap spare).

So there you go......

1. 12V cut out and standard summer/winter charge
2. 12V regulator
3. Solid state conversion
4. schottky diode and rheostat or resistor


To be honest if I did another one I would just do as Malcolm suggests and fit a 12V cut out and enjoy the car!

Best of luck

Steve

All good stuff chaps, and thank you very much for the advice. I did actually buy a solid state box last year but then read about the b*ggeration factor if it packs up some dark wet night in the middle of nowhere. Glad now that I waited. Shall pursue Malcolm's course of action and report back in due course. Nick

What's the problem with electronic voltage regulators? My friend with an RP saloon bought two (one to fit, one as a spare) from Dave Lindsay in 1967. He finally had to fit the spare in 1990 and sent the failed unit back for repair, it was returned repaired F.O.C., and it lives under the passenger seat. Can't complain at that. Dave

Dave

To be fair they should be OK.
Mine came with instructions that stated quite clearly that the unit would be damaged by setting the charge current to high, BUT to protect against this happening a fuse was supplied. The conversion was designed to use this fuse as protection and the instructions made an issue of making sure you had to fit and use this fuse. For instance charging a flat battery would be fatal for one of these devices unless the fuse is fitted.
I was put off by stories of other peoples failures, my own unit did not fail and I still have it. I think most people are put off by the fact that the unit is "potted" and therefore unrepairable by the roadside or even in your garage. Anything that is not repairable or "bodgeable" is probably not the sort of thing a Seven owner would fit, given the sort of person who owns and runs our type of car!
The unfixable black boxes are probably best left to the modern brigade .


Steve.

Hi Dave, my experience ( or rather someone else's experience ) was while we were on the Zuider Zee tour in Holland back in the 90's. One of the cars had a 12v system with electronic regulation which failed during the first day or two. Never mind, he was carrying a spare unit ( at a cost as they seemed to be the same price as the mechanical cut-out ! ).

So this was fitted and off we went again for a lovely time. Unfortunately this replacement unit failed as well so he had to rely upon his battery only to get us from the centre of Holland all the way back to Cornwall. That has given me a bit of a downer on electronic units in a Seven with all the inherent interference create by unsurpressed electrics.

With a mechanical cut out you can usually get something working by hook or by crook, an electronic unit NO Chance.

Any way, if they are that good why is it necessary to carry a spare? How many people carry a spare cut-out around with them in the car?

( PS I do carry one ! )

I have heard that there is an inferior unit to the Dave Lindsay one on the market.
I have used a pirated Volvo (only the best) alternator regulator with the 6 volt cut out modified for 12 volts for the last 20 odd years. The criteria was price-they are £4.50 each. In that time I have experienced one failure and the get you home fix is disconnect the regulator and replace it with a mini heater fan rheostat (from my first 12 volt conversion in 1968)which gives manual control. The rheostat lives under the drivers seat when not in use, I trust that fulfills the Austin 7 tradition. Dave

Great stuff Dave .

I too use a rheostat for manual control...or as some of the Cornwall club call it "the Simmerstat"!!!

How does your Volvo reg wire in? My electronic unit required conversion to two brush operation, meaning that in the event of failure it was difficult to "bodge" a fix to get you home?

Steve.

My 12 volt conversion is as follows:
1)Remove and store third brush assembly
2)The field connection to the third brush is earthed
3)Remove field resistor from housing on dynamo
4)The regulator has 3 connections D, F and E. D is connected to D on the cut out, the field connection to the ignition switch panel is removed and connected to F on the regulator and the E is connected to E on the cut out.
5)A resistor of about 30 ohm (I can't remember the exact value without removing the cut out) is inserted between the voltage coil and the E terminal in the base of the cut out to convert it to 12 volts.
This conversion is on our RNs which have the C35A dynamo with field resistor mounted in the dynamo terminal box, a CF1 cut out and the Lucas SM5 switch panel so the instructions will vary for later cars with the field resistor under the later cut out.
So if the cut out packs up I disconnect the wires from the D and F terminals on the regulator and connect them to my mini heater rheostat and adjust it to give the desired charge.
ONE WORD OF WARNING WITH THIS SET UP IF THE BATTERY IS FLAT DRIVE GENTLY (DON'T GO RACING THE ENGINE IN LOW GEARS)TO GRADUALLY RECHARGE THE BATTERY AND MAKE SURE THE FIELD FUSE IS 6 AMPS MAX AS LUCAS SPEC. WITH THIS SET YOU CAN GET ABOUT 18 AMPS OUT OF THE DYNAMO AND YOU WILL COOK IT IF YOU TRY TO DO THIS CONTINOUSLY. Having said that neither Sue nor myself have seen one off in 20 odd years however I never fit the strap over the dynamo brush gear to allow cooling air in, I know dirt will get in but I live with that.
That is where the more expensive Dave Linsay unit has an advantage because they are set up not to overload the dynamo. Dave

Sound interesting Dave, the conversion I used had a small potentiometer to adjust the max charge rate and a fuse for protection as well.
I had originally intended to just carry a schottky diode for a cut out and a charge limiting field resistor for roadside bodging and leave the solid state unit on the car until it broke (if it ever did), as it did a really good job of regulating the charge. Of course I got carried away and fitted the "simmerstat system" to give manual control for no apparent reason?
Maybe I should put the working solid state device on ebay!!

Steve

Steve,

If you put it on Ebay and describe it as 'Rare' or as 'originally from an Austin Seven' I am sure someone will pay an inflated price for it.

On a more sensible note. Whereas I applaud those who go before most of us in using electronics to perfect 12v systems I do feel that it is somewhat getting away from the general principles of the Austin Seven in that everything is simple and uses 'nuts and bolts' technology. If we can achieve 12v using the same technology as Herbert Austin & Stanlet Egde used then it seems to me to fit the general priciples of an A7.

I am certainly not an 'anti electronics' person having dabbled in electronis for 20 odd years and had built a computer from bits ( not a Sinclair kit ! ) back in the early 80's to my own basic design.

If we take the ' electronics' theme too far will we end up with an Austin Seven with electronic ignition, an electronic management system, ABS brakes, electric windows and central locking? We might just as well join the 'classic car' brigade and drive an Austin Montego.

Malcolm

I do believe the Montego had a digital speedo?
Some of the Cornwall club are using digital bike speedos?

Scary stuff.... perhaps armageddon is not that far away!!! .

Steve.

p.s I reckon The Colander is more "tank tape and self tappers" than "nuts and bolts".

My 12 volt system is one that evolved over many decades, during the sixties I was content with just 6 in my RN. The aquistion of a Cambridge special in 1968 was the start of the change, I wanted to see where I was going so visited Lucas in Manchester to ask about converting a C35 dynamo to 12 volts. Their answer was it can't be done just made me all the more determined. The special took to the road in 1970 with a 12 volt C35 2 brush dynamo and lucas regulator set up by a specialist, however the dynamo soon cooked because the regulator didn't like the high field current. So I reverted to a 3 brush 12 volt dynamo with mini heater fan rheostat for charge control and a 12 volt CF1 cut out, this system worked well for 11 years till I part exchanged the special for another RN running on 6 volts. Then one day the boss asked me to take his alternator in for repair/exchange at a local auto electicians. The guy there saw my 7 and the subject soon got onto 12 volt conversion and he produced the AVR saying this will solve all your problems and it did. I have noticed it reduces the load on the dynamo, most of the time on a long run the ammeter is on zero, the dynamo is producing what the ignition is using. After stopping at traffic lights the ammeter rises up to about 6 amps just before changing up and by the time I'm in top gear it's back at zero.
One thing that I didn't appreciate in the sixties was the importantance of the rear window blind as an aid to seeing where you are going at night.
Sat Nav, ABS, etc won't find their way onto our cars but I am a firm believer in see and be seen, after all I'm only following the example of the National Railway Mueseum. Their exhibits which take to the national rail system have eletric lights and air brakes.

Dave, I am sorry if I have seemed critical of your methods for 12v, I didn't intend to be so. I have taken the route of simplicity but from what I understand of your method you seem to have a system which is kinder to the battery.

I am very much with you in the 'see and be seen', I have had indicators on my cars for many years ( not as long as you as I only got my first Seven 10 years ago ) I soon realised that the indicators need to be large and obvious, there is no point on making them small to keep the car looking almost period; following motorists will not readily see them and the end result is a modern in your back end when you think you are letting them know you are turning.

On my RK saloon I have 7" H4 60/55W halogen headlights, every time I go for my MOT the man comments that they are as good as most modern cars. They have a very precise 'cutoff' line for the dip beam so can be set reasonably high making driving at night very easy. Once the rear blind is lowered the road ahead is very clear.

60 watt 12v bulb uses the same amps as a 30 watt 6v bulb!!! ( 5 amps in the above examples )

All this thanks to 12v. I can understand why people stay at 6v for originality but really if you intend to make full use of your cars then 12v is the safe way. Will we see you at Guildtown again Dave ?

Thats OK, I didn't relly think you were serious, heaven forbid a Montego.
Yes one of our cars has 55/55-watt headlights (these are modern replacement reflectors and I haven’t located any smaller bulbs) but I really think such high wattage bulbs put too much load on the dynamo. That is 120 watts for 2 headlights and 2 tail lights-10 amps plus 2 for ignition, total 12 amps from a dynamo rated at 8 amps. We are skating on thin ice and that’s without taking into account indicators, stoplights and wiper motor, although with the 22 FZB I use a vacuum wiper motor but these don’t work well with the 26VA. I wouldn’t recommend these for an electrical novice, we get away with it by such moves as leaving the brush cover strap off to allow cooling air into the dynamo.
The other car has the original RN Lucas Graves reflectors fitted with 35/35 watt halogen bulbs and these are as good as the 55/55watt tungsten bulbs and bring the load on the dynamo down to a more respectable 80 watts for lights, 6.5 amps plus 2 for ignition, total 8.5 amps. Bear in mind the dynamo was originally intended to supply two 12 watt headlights one five watt tail light and the ignition-7amps on 6 volt RN saloon.
With this in mind I have tried various mods to relieve the load on the dynamo:
1) The car with 55-watt headlights has 3 light settings main beam, dip beam and dim dip. This latter feature switches the 2 headlights into series, which is OK for driving in lighted areas but has the problem that if one bulb blows the other goes out. Not good.
2) The same car has 20 watt halogen sidelights which on the RN are in the headlight and give a good light for town driving, better than 1 above, and reduce the load on the dynamo when you are stopped in traffic. I took this route because side lights are really now parking lights.
3) I was at one time considering fitting an alternator on the prop shaft but I gave that up, I preferred the challenge of getting a quart out of a pint pot.
I see my entry for the 3 June has an error it says "so if the cut out packs up" when it should say so if the regulator packs up.
This posting has proven fruitful, it's made me look for some 35/35 watt halogen bulbs, these are available from classic and vintage bulbs-an Australian organisation.
Unfortunately for the first time in many years work will prevent us attending Guildtown, enjoy yourslves Dave.

One point to bear in mind is that people seem to be fixated on having the discharge current always balanced by the charge current. This is not usually necessary unless you do a great deal of night-time motoring. Provided that you have a reasonably decent battery, you can let this 'reservoir' supply some of the load. Of course, you must top it up again, either by daytime running or from a battery charger.

David

Well, I have all the bits bar the battery so Saturday will be 'give it a go' day. On the subject of lower wattage halogen bulbs, I recommend a call to Staffordshire Vehicle Components (http://www.s-v-c.co.uk/about.html). Steve, the boss, is entirely sympathetic to the needs of 'older' vehicles and I have just received some 12v 35w/35w H4 halogens from him, plus the other more standard bulbs to complete the conversion. Nick

Malcolm - A little more guidance if poss please. Have now fitted the RB106.
1. I assume that I can ignore the F2 wire from the ignition switch (as it is now a single rate of charge governed by the regulator rather than summer/winter switching) and connect the F1 wires from ignition switch and dynamo to the F connection on the regulator/cutout?
2. There is no obvious fusing within the RB106, unlike the 6 volt cutout it is replacing. Is there a need to fuse the dynamo at all?
3. I take it that the A and A1 connections are for auxilliaries and are live when the ignition is on?

Sorry if this is awfully basic stuff but I really don't want to make a mess of it!

Nick

Success! All wired up and working fine. Regulator/cutout doing its stuff - as a checked by a friend who understands these things. Only concern is that the new 12v coil is getting very hot. I'd expect warm but not hot. Has anyone an idea of what might be the cause or is it to be expected? Nick

Nick - re. your 3 questions for Malcolm, he might be able to reply , but I am aware he has some commitments over the next 8 days that might preclude him from replying, so please do not think he is ignoring you. (I know what I'm treying to say, even if it has not come out onto the Forum right).

Sandy

Nick
Re the hot ignition coil. I know that most moderns before electronic ignition had a ballast resistor in series with the coil. This resistor was there to give a higher output while starting when the voltage was lower due to the starter motor. Once the engine was running the resistor heats up and less current flows to the coil.
If your coil was designed for a resistor and you don't have one you will get a hell of a spark all the time and a hot coil. This resistor could be in the form of a light bulb.
Hope this helps
Pat

Pat - Thanks for the ballast resistor idea. I bought one at Luton's Festival of Transport today and tried it when I got home. Result? Complete refusal to start... Not wasted though as I put it on the 6v trumpet horn and now have more decibels than I can stand!

Shall be trying an alternative coil in due course in case the new one is faulty.

Nick,

The Rb106 is not a route that I took so I am unable to answer your questions re the wiring. Hopefully someone who uses this method will be in touch. Do I take it that you have converted to 2 brushes in the dynamo?

As to the coil getting hot, it sounds as if it may be the ballast resistor type, there were several sizes of ballast resistor which ranged from 2 to 5 ohms ( I think ! )so if you are using the wrong value when you tried the ballast resistor you may have reduced the voltage across the coil too much.

I would be inclined to get a standard 12 volt coil of the type used on the early Minis and Triumph Herald / Vitesse.

Happy motoring with 12v.

I know some feel that 55w headlights are too much load on the dynamo but they are actually drawing the same current as a 27w bulb at 6v and many Austin Sevens are using 35watt 6v bulbs so 55w at 12v is still kinder to the dynamo.

If you are really concerned then you will find that you can easily get 12v LED replacement 'bulbs' which only draw 5w for a 21w equivalent. Do check that they are suitable for your lamp fitting as a majority of the light comes from the top of the LED 'bulb' not from the side as in normal bulbs.

About a year ago I helped fit a 12v charging conversion to a friends Ulster. It sounds like the one Steve Martin refers to.. Two brush mod and a tiny silverbox Of tricks all protected by an 8amp fuse. Much was made in the fitting instructions about not letting the battery go flat as it would either blow the fuse continuousely or at worse damage the unit.WEll.... It has been damaged! and he has lost all the paperwork. Does any one recognize the setup and can give me a name and nunber of supplier?? Thanks Mac