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Jeep conversion to 12v (I finally got fed up with 6v !!)

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Finally got fed up with my Jeep not starting so I converted it to 12 volts. I’m sure somebody has already explained how easy it is but I thought I would jot down a few lines on how I did mine.

 

 

I totally rebuilt my jeep from the chassis up about 4 years and wanted to stick to 6 volt but a couple of years later the battery wasn’t quite good enough to start it and I have been forever having to use the starting handle for the last 18 months. I tried everything I knew to stick with 6 volts and make it work reliably but basically I don’t drive it enough and you can’t seem to buy a good 6 volt battery these days so I took the plunge and brought myself into the modern world.

 

 

The conversion to 12 volts was easy and only cost me about £150 including a decent battery. Lots of people I spoke to have had different ideas but the following worked for me.

 

 

1. Regulator. I bought an old style Lucas 12 v regulator to fit a Land Rover (also used for many other older Morris Minors, Austins, etc.). I used the type with screw in connections so I could just cut off the existing larger ring connectors and strip the wires bear but you could use the one with Lucar connectors just as easily. This was £25 new and I fitted it in place of the original, some people I have spoken to have stripped the insides of the old one and fitted this type inside as its about half the size so it looks original but I couldn’t bring myself to do this as my 6v regulator was brand new when I rebuilt the jeep and will live it not looking perfect.

2. Connect as follows: The Old Regulator has Field, Arm & Bat connectors with an earth to the case. The new Regulator has E, D, F, A, A1.

a. Field wire (Green wire from the small connector on the Dynamo, which is the one nearest the Regulator). Connect to F.

b. Arm wire (red/white lead with larger connector on the Dynamo, which is the one nearest the block). Connect to D.

c. Bat wire (Red/White lead which goes to under the dash) Connect to A.

d. Earth wire from the Dynamo. Connect to E. I also ran a wire from an earth on the chassis to E as well as you can’t have too many earths !!

e. A1 is spare which you could use for any other non ignition switched feeds you need if you wished.

3. Dynamo, nothing needed here as it will push out as many volts as you need and is of course controlled by the Regulator. I did actually have a problem as it didn’t charge when I started it on 12 volts. I took it into Autoelectrical in Glastonbury who sorted it, it turned out to be an earthing fault. I think this was due to me cleaning the brushes and when I put them back in I managed to mis-locate the brush wires and cause an earthing problem (I should have left well alone !!).

4. Ignition. Replace the ignition coil with a 12v one, cost £10. I had a Jolly Engineering electronic ignition fitted which was an earlier failed attempt to solve the 6v starting problem, I had to remove this and go back to the original points as it is wired for 6 volts and would have blown if I’d used it on 12v. Good old fashioned points work well on 12 volts so no need to change.

5. Headlights, this nearly caused me a problem as 12v 5 ¾ sealed beam units (5731) are no longer available. However Autoelectrical had some Halogen bulb conversion units for £35 a pair which fit the headlamps bowls once you slightly bend the three mounting tabs through 45 degrees on the lamps so they fit nicely. Connectors are of course the same so no re-wiring just blank off the side light hole in the lenses. The bonus is halogen lamps instead of 6v candles.

6. Front lights. I have four standard marker lamps on the front, 2 as sidelights on the tops of the wings (I have the Jeep in British markings, the Brits fitted them here) and two in the usual places in the grille as indicators with amber lenses in. These were straight 12v bulb replacements.

7. Rear Lights. When I rebuilt the Jeep it removed the black outs from the lower rectangles and fitted amber lenses and used them as indicators. I removed the sealed lenses/bulbs and cut the bulb ends off and stuck the lenses into the mounting ring with clear sealer (as the bulb ends hold the lenses in place normally but as you just cut them off they will be loose). Standard 380 & 382 bulbs then fit into the holders.

8. Dash lights, I had fitted 12v ones on rebuild anyway but a straight replacement.

9. Flasher Unit. Straight replace with a 12v unit. I did have a problem I think caused by the bulbs being low wattage which meant they didn’t trigger the unit. When I plugged in a trailer board to the trailer socket I have fitted hidden under the rear cross member the extra bulb and wattage caused the unit to work fine, a heavy duty flasher unit cured this.

10. Battery. I found a black cased heavy duty battery for £70, part number 030 fits the tray perfectly and is the largest one you can get in there but other cheaper sizes are available just a bit smaller.

 

 

Job done, now starts instantly, lights are great and I don’t have to worry about trailer lights. No other changes are needed, the wiring is fine, 6v actually needs double the ampage of 12v so is more than heavy enough if in good condition. I’ve been told that the fuel gauge will read wrong unless you fit a resister but I have to say I have never known a Jeep fuel gauge be right in any case !! The starter is fine unless you keep it turning over for too long but it now starts after about a second so should be fine, apparently you can get a better starter bendix spring if it plays up.

 

 

Hope that is useful, its certainly made a very big difference starting both hot and cold. Some pictures below for those interested. :D

 

102_5855.jpg

102_5858.jpg

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There seems to be a MWO for this: (I figure its an actual MWO.. not sure)

 

MWO-G503-W7

 

Most jeep owners will tell you that 6v works fine. Your grounds and starter may need attention.

 

What is the end play on your starter shaft? The starter has bushings that will wear and cause significant run out and drag the shaft.

 

I just cleaned the commutator on my starter and reset the timing (after a valve, bearing and ring job) and it pops off in 2-3 rotations of the engine.

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Thanks for your reply, I googled MWO-G503-W7 and found a comprehensive 16 page instruction book that made interesting reading. This seems to include new starter, generator, pulleys, twin batteries between the seats and loads of other new parts, seems its for high power radios to be run from the Jeep.

 

I didn't touch the starter so don't know about the end play. Somebody did tell me that if I get trouble with the starter Bendix then a stronger one is available as the starter really does turn over quicker but so far so good. Ground (Earth) wise when I rebuilt the Jeep I over did the earth straps anyway and I have a main one which goes direct from the battery to the chassis and then onto the engine in one run plus a gearbox to chassis one and the two I mentioned to the regulator so its most likely a bit overkill.

 

I also did check the timing as when I removed the electronic ignition I had to re-time it so that's right.

 

Andy

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6 volt vs 12 volt is the eternal quandary with jeeps. I have had jeeps that started fine on 6 volt and some that I converted to 12 volt to cure bad hot starting, on reflection I suspect it was really a case of worn out starters/ bushes.

 

There is a very sound case in today's world to change to 12volt for convenience of parts supply ect, however part of me still thinks that if 6 volt was so unreliable from new then an industrial might like the US would have changed to 12 volt pretty quickly.

 

I'm interested in the fact that you are still using the original dynamo, what amperage to you see on charging?

 

Pete

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Good post, thanks for sharing! I was toying with the idea with mine, horrible starting, even with brand new battery and starter. You have convinced me to take the plunge!:tup::

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Pete

 

You make some good points abut 6v, in fact I had a 6v Dodge a few years back and that was always fine. The starter on my Jeep was new 1,000 miles ago and I cleaned the brushes etc, I also checked the floor mounted starter button as I have heard of them not being good enough and checked/rechecked the wiring, earths. I also altered the timing around and fitted a Jolley Engineering electronic ignition as this draws less voltage on starting all to no avail. There was enough volts to turn it over but none left to charge the ignition and in fact sometimes it would start just as you released the starter button and the engine was still just turning.

 

Having spoken to a number of auto electrical people who have all said the same thing they basically don't make decent 6 volt batteries today, my Dodge had a very very old battery on it which just went on and on. I think you are right in as much as their never used to be a problem but 6 v was main stream and batteries were up to the job, today they are made cheaper with less amps so as soon as the battery is anything less than brand new it becomes an issue, also I only do about 400 miles a year which is no where near enough even with a trickle charger to keep the battery 100%.

 

Regarding Amps output it pushes out what the battery needs so the gauge shows actually as it would with 6v as the Amps are no different, it tends to show lower as less is taken out of the battery after starting so drops back to near zero quicker. The Dynamo will ultimately push out about 50volts if it was unregulated its only the voltage which is different, the amps and watts are no different.

 

Rick

 

Glad I have drawn you to the dark side, I have of course kept all my 6v stuff just in case I want to go back one day !! Please let me know if you want more info or pictures. I didn't mention the horn, I have kept the 6v one which is now louder !! but I should change that as well in case it doesn't last.

 

Regards

 

Andy

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Andy

Your point about modern 6v batteries is interesting, and I suspect you may well be right.

 

I'm just at the point with another jeep where I need to decide between staying with 6v or biting the bullet and going for 12v. The major stalling point (pun intended) for me with 12v has always been replacing the dynamo with something that just doesn't look right.

 

Up to the point of reading your post I have never re used or heard of anyone re using the original Auto-lite dynamo, so I'm very interested what you have done. Did you have to adjust the cvc that you bought to match the Auto-lite output?. Another question if you don't mind, what is the amp hour of the 12v battery you are using?.

 

Regards

 

Pete

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The OPTIMA line of 6v glass mat batteries are exceptional power storage devices. They are not traditional lead plate batteries.

 

If the looks bother you there is a fake 40's Ford battery box that they will fit in.

 

[TABLE=width: 100%]

[TR]

[TD=class: pdSS]Cold Cranking Amps

[/TD]

[TD=class: pdT]800

[/TD]

[/TR]

[TR]

[TD=class: pdSS]Cranking Amps

[/TD]

[TD=class: pdT]1000[/TD]

[/TR]

[/TABLE]

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Pete

 

No I didn’t match the regulator with the Dynamo, I remember from my apprentiship in mechanics, many years ago that you would have to ‘tune’ the Regulator to the Dynamo but it seems that modern ones are better factory set in the first place. An electronic version is also available which should be better again but cost more.

 

The battery is 570amp constant cranking but as the engine actually starts easily and a Jeep doesn’t have much in the way of electrics fitted I think a smaller battery/lower amps would work fine, 12 volts should give you some ‘slack’ where as all the amps in the world won’t make up for 1 or 2v drop in the system with 6 volts.

 

The dynamo charges about 14.1 volts at about third to half revs.

 

The Optima 6v battery mentioned in the next post looks interesting, that should be more than enough power as long as the wiring is ok and you can keep 6 volts reaching the starter.

 

Andy

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Pete

 

No I didn’t match the regulator with the Dynamo, I remember from my apprentiship in mechanics, many years ago that you would have to ‘tune’ the Regulator to the Dynamo but it seems that modern ones are better factory set in the first place.

 

Andy

 

Thanks for the reply Andy this is all interesting stuff, could I ask a couple more questions please,

 

1 what is the model number of the Lucus cvc you have used?

 

2 does the dynamo run hotter with your conversion?

 

I'd be very interested to hear how the conversion is working when you get a few miles on the clock, could you post results please?

 

Many thanks

 

Pete

Edited by Pete Ashby
additional question

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Pete

 

The old Lucas part number is RB106, follow this link, http://www.autoelectricsupplies.co.uk/product/460/category/83 you will see this one has screw connections as I used but they also list others with spade connections which does the same. I got mine from a local company called Autoelectrics in Glastonbury so they are around if you look, plus Autoelectrics were very good with advice.

 

Interestingly they also do a 6v version of the same thing which costs 4 times more !!

 

It doesn’t seem to run hotter but I can’t say I took any notice of what it was before. After 40 miles it was only warm to the touch and I guess that was mostly down to the engine heat.

 

Apart from testing in the workshop I’ve only done one 40 mile trip which I did today, it all seems fine and it was great to stop when the engine was hot, leave it 10 minutes and then it started again after about half an engine turn. I will keep you posted as time goes on.

 

Gary

 

Regarding the conversion manual if you follow this link http://jeepdraw.com/MWO_ORD-G503-W7-Convert-6V-to-12V-1948-52.pdf you can download the manual in PDF from jeep-draw for free.

 

Andy

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Should we assume that the main problem with hot starting is down to reduced voltage at the coil caused by extra drag on the starter motor caused by either worn bendix etc, or as some suggest by the later type of oil control piston rings used nowadays?

 

In which case what about the old ploy of putting an alternative 6v supply on the coil (e.g. dry cell batery) to avoid this voltage drop?

 

Incidentally I've measured just 3 to 4 volts at coil when cranking - small surprise at the resulting poor spark!!

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I Know quite a few jeep owners who have added an extra battery on a switch just for the coil for that extra boost, its totally independant, a motorcycle battery.Once jeep is started it then runs on normal feed. Seems to work very well.

 

Howard

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Should we assume that the main problem with hot starting is down to reduced voltage at the coil caused by extra drag on the starter motor caused by either worn bendix etc, or as some suggest by the later type of oil control piston rings used nowadays?

 

In which case what about the old ploy of putting an alternative 6v supply on the coil (e.g. dry cell batery) to avoid this voltage drop?

 

Incidentally I've measured just 3 to 4 volts at coil when cranking - small surprise at the resulting poor spark!!

 

Coil robbing can be and often is the problem with jeep hot starting, however it can be a compound issue where the increased compression slows the cranking speed of the starter motor, slow cranking will not clear petrol vapour in the choke tube of the carb so you end up with an over rich mixture and a very weak spark due to coil robbing caused by the starter motor that is now drawing something near it's maximum amps. The windings heat up and the resistance goes through the roof, and so it goes on until that fateful last grrrruf umph from the motor as it finally stalls at TDC.

 

By this time the plugs are fouled and it's time to take the air horn off the carb, blow down the choke tube to clear the petrol vapour gently pull the hand throttle out full and get the handle from behind the back seat accompanied by lots of bad language.

 

I'm not surprised at 3 to 4 volts at the coil, as you say NOS, small surprise at the resulting poor spark.

 

Been there done it too many times, usually in the most embarrassing situation possible.

 

Pete

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Pete

 

The old Lucas part number is RB106, follow this link, http://www.autoelectricsupplies.co.uk/product/460/category/83 you will see this one has screw connections as I used but they also list others with spade connections which does the same. I got mine from a local company called Autoelectrics in Glastonbury so they are around if you look, plus Autoelectrics were very good with advice.

 

Interestingly they also do a 6v version of the same thing which costs 4 times more !!

 

It doesn’t seem to run hotter but I can’t say I took any notice of what it was before. After 40 miles it was only warm to the touch and I guess that was mostly down to the engine heat.

 

Apart from testing in the workshop I’ve only done one 40 mile trip which I did today, it all seems fine and it was great to stop when the engine was hot, leave it 10 minutes and then it started again after about half an engine turn. I will keep you posted as time goes on.

 

Andy

 

Thanks for the info Andy, I look forward to hearing how you find the conversion after you get a few miles on the clock.

 

Regards

 

Pete

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NOS

 

You’ve opened a can of worms with that question !! There will be a lot of different opinions on this subject but I’ll give you my spin on it and its not a short answer I’m afraid so please bear with me and I’m sorry if I explain some things that are obvious and you may know already.

 

There are a number of different things happening in an engine to stop it starting and they act together sometimes.

 

When starting from cold oil is a lot thicker and causes a lot of extra drag on all the bearing surfaces so its very tough to turn the engine over, this draws a lot of power so everything else has to be perfect, battery, wiring, timing, fuel mixture, choke setting, compression in order for it to start especially in the winter with cold air temperatures. Mix all that with the fact that an engine doesn’t want to run when cold its all a recipe for disaster so with only 6v it only takes a little for it not to start as there is no leeway, my view is that when 6v was main stream 6v batteries were a lot better quality than they are today and this is enough for it to be an issue.

 

Therefore all the power available to going to the starter nothing is left for the coil to fire the plugs hence as you say on 3-4v at the coil, you can sometimes see this when you crank the engine over and it doesn’t start, you release the starter and it catches and fires just before the engine stops turning over. This is because the starter has stopped drawing the power and its suddenly available for the coil whilst the engine is still just turning and it fires. A Jeep engine is in fact normally a good starter so again you can easily (ish) start a Jeep on the starting handle because all the power is going to the coil and it only takes half a turn once the fuel is there (always worth hand pumping the fuel into the carb using the lever on the fuel pump).

 

The ability to turn an engine over when very cold is demonstrated by the Russian’s, WW2 & post war Russian tanks smoke a lot because they are fitted with undersized pistons giving a larger operating gap with the bores thus allowing them to turn over when starting from very very cold, the side effect of the larger gaps between the piston rings and the bores means oil is pumped up and burnt hence the smoke. During WW2 German tanks had a real problem in winter in Russia because their precision engineering meant they wouldn’t turn over and start when cold, the answer was to lit a fire under the engine and keep it burning all night !!!

 

So when its hot and the cylinder head is hot and the oil is runny you hit the starter and it spins a lot quicker than when its cold it should be fine but it still won’t start. You often get something called ‘Vapor Lock’ as described by Pete. In a simple fuel system like a Jeep you stop the engine and if you leave it about 10 minutes it won’t start because the fuel in the carb or sometimes in the fuel line has evaporated and turned to vapor with the heat of the engine, this isn’t helped in a Jeep because the carb are right on top of the hot exhaust. The vaporized fuel causes a ‘bubble’ in the system and needs to be cleared as Pete states which works most times or left to cool down. If you stop a hot engine and re-start it straight away its fine because the fuel hasn’t evaporated yet and if its left about 45 mins its cooled enough for the fuel to turn back to liquid fuel.

 

To get a bit technical vapor compresses but liquid doesn’t so then the engine turns over slowly the mechanical fuel pump can’t pump enough fuel pressure through the ‘lock’ and it doesn’t start. As 12v has a bigger kick turns the engine faster and it pushes the lock through instantly, it doesn’t take a lot. Once its running it can be as hot as you want but as the fuel is running its fine and will keep going.

 

In hot climates its common for electric fuel pumps to be fitted, sometimes in addition to a mechanical fuel pump so when you switch the ignition on the electric pump pushes fuel through with a bit of grunt before you turn the engine over (I had one fitted to a Dodge WC63 a few years back that had been used by the French Army in North Africa). More modern vehicles have an electric pump with a return line so fuel is always being pumped to the carb and when the carb is full it flows back down a return line to the tank so you never get the problem where as an old fashioned single line stops flowing altogether when the carb is full and thus is susceptible to getting hot.

 

A lot of others things such as changes to oil (stickier these days), us all not using the vehicles as much as they would have been, higher octane fuel, better engineering (tighter bearing tolerances), etc. etc all don’t help but I feel these are the main reasons.

 

So you end up with the issue that it won’t always start when hot or cold for two different reasons, it only ‘just’ doesn’t start but it amounts to the same thing. I guess if you really wanted to stick to 6v you could have a separate battery as you suggested for when its cold and an electric pump for when its hot and as long as everything else is good is likely to fix the problem. 12v gives you enough of a safety margin to be much more reliable and is the main reason 6v died out and 12v is still used to this day, people just don’t like using a starting handle anymore. If only life was simpler !!!!!

 

Andy

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Converted several jeeps to 12 volts.

 

I did not want to use Lucas parts so with some research found a modern electronic regulator that you can either hide in the existing regulator box ( so everything looks as standard) or just hide it somewhere else ( I find behind the air cleaner is a good out of the way place and you have to look hard to see it.

 

Best thing is you get a good battery charge even at engine idle

 

I now offer these as kits if anybody is interested http://www.kauto.co.uk/shop/index.php/cPath/43_54

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Dear all

 

I was asked during this thread to come back and let everybody know if this 12v conversion worked over time. I'm happy to report all is good, I've completed a good few miles now and not had a problem with the original 6v dynamo and starter working on 12v. It starts instantly hot or cold and has been a breath of fresh air after having to use the starting handle much of the time.

 

I now just need to hide the 12v regulator in the old style regulator case and cover the battery with something or put it in an old case so it looks right.

 

Andy

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Andy thank you for coming back to this thread with your findings very interesting indeed with regard to the success of using the original generator on a 12 volt system.

Food for thought

 

Many thanks

 

Pete

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Dear all

 

I was asked during this thread to come back and let everybody know if this 12v conversion worked over time. I'm happy to report all is good, I've completed a good few miles now and not had a problem with the original 6v dynamo and starter working on 12v. It starts instantly hot or cold and has been a breath of fresh air after having to use the starting handle much of the time.

 

I now just need to hide the 12v regulator in the old style regulator case and cover the battery with something or put it in an old case so it looks right.

 

Andy

 

This page might interest you.

 

http://www.jalopyjournal.com/forum/threads/putting-a-12-volt-battery-in-a-6-volt-case.756016/

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Pete

 

No problem, glad it was useful.

 

MatchFuze

 

Thanks, I'll look into that further.

 

Andy

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