Converting from 6v to 12v

[Sam Buchanan]

I've never considered the headlights to be a problem on my 6v P15. I installed common halogen sealed beams and a new dimmer switch and freshened up the terminal block behind the grill. One of my favorite runs is an after-dark drive from my brother's house in the hills and deer are plentiful. The lights are just fine for the speeds the car was intended to be driven even on a major highway (55-60mph).

Edited April 1 by Sam Buchanan

[Sniper]

When I first started driving incandescent headlights were the norm.  In 1986 I bought my first new car, a Daytona.  It had halogen bulbs and I thought they were the greatest things.  Many years later, and many rides later, I got a set of Hella H4 housings for my daily drier, what a difference.  Still halogens but with good optics, not your off the shelf mass produced good enough stuff like what I had been using since forever.

 

For the Cambridge I stepped up to good housings sporting LED bulbs.

 

The difference was similar to going from incandescent bulbs straight to the Hellas (skipping regular halogens).

 

I would venture to state that the head lights in my 51 are now as good as the headlights in my 2015 BMW.

[kencombs]

I started working on cars for money in '59 at 16 years old.   Service stations then Dad's salvage/garage in '61.  Lots of 6v cars on the road then and lots of jump starts, battery charges and/or replacements along with cables in cold weather.   I went to work at a big airline maintenance facility in late 61, but still worked on cars in my off hours.   At the end of the 11pm-7am shift the huge parking lot would always have some jump starts in progress after a frigid night.   So, yes  6v worked, but needed help. 

 

Truthfully, cars of the 50s were not as reliable as today's.   But expectation were lower because of the owner's experiences.   IMO, people wear rose colored glasses when using hindsight.   Those expectations color the real experience.

 

[Veemoney]

8 hours ago, kencombs said:

At the end of the 11pm-7am shift the huge parking lot would always have some jump starts in progress after a frigid night.   So, yes  6v worked, but needed help. 

 

Truthfully, cars of the 50s were not as reliable as today's. 

All true and even in the mid 50s when cars switched to 12v we still were seeing the jump-starting masses well into the 70s on frigid mornings. Cars didn't have idiot lights back in the 50s like they do now. Also had just a few folks that subscribed to the failure mode then fix it mentality (I'll call this FM) and just say for some idiot lights don't help.

 

I believe the following were key developments that improved reliability and reduced frigid start issue Failure Modes:

• Electronic ignitions reduced point maintenance (FM= Improper point gap) and provided hotter sparks (FM= fouled plugs).
• Fuel injection optimized mixture settings for current conditions (FM= Improper choke setting for cold starting).
• On board computers sense and adjust all systems for starting, (FM= Flooding/lean fuel mixture, Running down battery due to incorrect settings during starting attempt).
• 6V and 12V batteries both had the same issue before sealed batteries came out. (FM= clean connections, correct size cable and properly filled)

They say 12v was chosen in the mid 50s to support the larger higher compression engines like the hemi motors in 1955 and moving forward.  My thought is the reduction in copper wiring size required for 12v cars reduced costs and was a driving factor in the decision to move to 12v. To Sniper's point once Detroit made the choice and moved to 12v, technology followed 12v and left 6v in the dark ages of the 50s. Ken's deduction for what he seen back in the 50s as cars not being as reliable is true but maybe not so much the fault of the 6v system but I would push some blame to human performance since after the switch to 12v the same issues were present in the later part of the 50s forward until the technology to eliminate the failure modes above provided noticeable improvements. If Detroit had stuck with 6v and the same technology advances were made cars would surely have become more reliable with 6v but heavier with copper and more expensive. 

 

In 2023 Tesla started deliveries of their Cybertruck that uses a 48-volt electrical system, reducing 70% of the wiring in the vehicle.  For those in need NAPA sells a 975cca 6v wet acid battery for $150 which should be enough to start a big V8 or any L6. Standard width and height just a bit longer case.

 

Just my rambling on a rainy day   

[kencombs]

3 hours ago, Veemoney said:

 Standard width and height just a bit longer case.

That sentence reminded me of the first auto 'work' I remember doing.   Must of been 6 or 7 and Dad had a late 40s Olds (I think, GM for sure).   He was replacing the dimmer switch but couldn't reach it from above and no floor jacks on the farm.   So he recruited me.   took out one of those long narrow 6v things that GM used in some cars.  In front of the firewall and down near the  frame rail.  With it gone, Dad stuffed me in that spot and talked me through removing and replacing that switch.  

 

On  your other observations, Agree wholeheartedly, especially the faulty human part.

[Sniper]

I can remember when I was a kid my old man having to bring the battery in during the winter on a 70 Buick Skylark. So yeah cold weather starts for 12 volt cars were problematic in many cases as well. And you may have a point about electronic ignition and other advances but you know what starts up on the coldest days no problem but I stay on top of the maintenance as well like anything if you ignore it long enough it'll quit working

[Tom Skinner]

Whether 6 or 12 Volt - its the owners choice. One point to make is, if one chooses to remove their old wire harness and use it as a template/pattern to make a new one with new wire (using a good service manual or wiring diagram as well) then a lot of electrical problems will go away especially if the harness on your car is shedding its insulation around the wires. I opted for Rhode Island Wire, Because I could. but looking at the old harness taken apart afterwards I could see how easy making one could be.

Of course this presupposes one has some electrical sense - which  my electrical abilities leave much to be desired. Either way nowadays both are expensive propositions if I have read this thread correctly. So here is a shout out to all that are changing over to 12V. 

Good Luck.

Tom

[Racerstev]

It was a battle, these things tend to snow ball. 
 

If I had to grade the DCM kit I would give it a 6 out of 10. The brackets and alternator fit well. That is before I swapped the water pump out. The fan cleared the alt at 1st but needed spacers to aline the belt and clear the alt after water pump replacement.  Wiring was easy. 
 

The coil was a bit of a learning curve. Seems you need either a 3 ohm coil or a 1.5 ohm coil with a ballast resister. They shipped a 3 ohm and a resister. So w/o checking and assuming they sent the right parts I put the resister in. No start… w/o the resister she starts right up. DCM was clueless i

on this btw. 
 

Light bulbs were next, It was imperative to keep the 39 headlights. 
they sent 12 volt bulbs, these fit but don’t aline with the contacts. A hour and a file cured that. 
 

Battery, a group 35 Optima will fit but the spacer needs to be removed. 
 

guess thats it, she starts like a new car. I now have the confidence to drive her just about anywhere close and have her start easily. 
Steve

[DJ194950]

How about a one stop kit?

 

https://www.ebay.com/itm/225551410030?itmmeta=01HVMCNJB8XZQBSJ8TC8PR5HK5&hash=item3483e9636e:g:fikAAOSwWS5kSWje&itmprp=enc%3AAQAJAAAA8Np1PQWowjXOm5dtALtv4izyH2ReAQ%2Fr8oJceDy6VJu81hgtEf5REuuNGNoT8wsuARJwB%2BO5yLDPiykyXh0%2BcXqYJ3XDN5b%2BXIuKzyvXZly39Mo%2B1qot5kgamQwivKswaVwVv7I5B407HMRk17YL1hKieanHjqQqVCIhVMgzul2V2pN%2BXf0S9C%2Fh3BjCGf7PpXYUAIngMiYngZRc--rqevLNq4sRrOpRI41W9%2BOMMQiPtxrNi2Yt6WlAGIj6vAM7RQ40tokzq12kJ6rCSM8sYwL5AXdvwrhENohSLjKXNqeY10Ep3F%2FdDC549jBlMfsb7A%3D%3D|tkp%3ABk9SR9yl1ozdYw

 

A bit expensive in my book!!!  🤑  😵

 

DJ

[Racerstev]

That’s 3 times what I spent. Seems to be alot of stuff you don’t need…

 

Oh, a word about the single wire alt. No problems, it charges fine at idle. 

[kencombs]

17 hours ago, Racerstev said:

That’s 3 times what I spent. Seems to be alot of stuff you don’t need…

 

Oh, a word about the single wire alt. No problems, it charges fine at idle. 

Even if one wanted to replace all that stuff, it is way overpriced.   Bet it could be bought piecemeal for under 300 bucks.

[Dodge_48]

Seems there are obviously several ways to skin this cat. 1) just change everything to 12v. On that approach, I saw a post that implied all they needed was a 1-wire alternator and bulbs. Well, that doesn’t consider the heater and wiper motors, the fuel gauge, horn etc. The kits are there for a reason. I know of 3 sources now that sell them, and they’re all around $750. 2) put in a hybrid system. I saw a post where the owner preferred the look of the 6v headlights at night. If you have a reason to prefer the 6v system but want improved cold weather starting, you could buy an 12v 1-wire alternator and a 12-6 volt converter to run everything other than the starter, safely. That would also be the quickest installation. The alternator might run you as much as $350, if you wanted it to look like a generator. If you’re resourceful and know where to find it, you can buy a 50A electronic converter and a spare for $75. Alternatively, if you want the advantages of 12v, you still need to protect voltage-sensitive devices, as mentioned above. You could buy the $750 kit, or protect the voltage sensitive-devices with a voltage converter instead of the resistance units, which can develop a lot of heat. You need to move the source leads for the devices to the converter, but that’s no more trouble than wiring-in all those other resistance devices. That’s what I did. It gave me the advantages of a 12v system, and provided protection for the horn, coil, , wiper motor, fuel gauge, and heater motor (if you haven’t already converted it to a 12v motor) for far less than $750. I also added an inexpensive fuse block under the dash for them while I was at it.

[Sniper]

I dunno, the heater motor is easily replaced with a 12v, the one I used on my 51 costs a whopping $31, new from RockAuto.  Since the insulation was failing on the original 6v motor this was a no brainer.

 

Wiper motor, you can buy a 10A 12v to 6v converter for $22 from Amazon, that takes care of the wiper if you have electric wipers, otherwise not an issue.

 

The only gauge that is voltage sensitive is the fuel gauge and that is only the later, non thermal types. Not sure it applies to the OP's 49 truck or not.  But if your fuel sender has more than 1 wire then it's not affected.  You can use a runtz resistor or just feed it from the voltage converter powering the wipers.

 

Swap the ammeter wires if going to negative ground. 

 

Bulbs

 

That's it.  Well you do have to swap in an alternator.  Not hard to do, not expensive and no fancy brackets needed.  In my case the 51 had 12v battery cables on it when I bought it, still was a 6v system.  Lot's of other hackery the OP's mechanic did.

 

If you have a ride that has vacuum wipers, no heater and the thermostatic fuel gauge then all you have to swap are the bulbs.  Almost so easy even a caveman could do it,

 

I had a guy stop by with a 51 Chevy that could have been my Plymouth's brother, black exterior, grey interior, coupes.  Anyway, he wanted me to convert it to 12v because his headlights were too dim.  After inspecting the setup turns out it had 12v headlights in a 6v system,  No kidding they were dim, lol.  I gave him my old 6v headlights and once swapped out he was happy.  Saved him a few dollars.

 

I don't really have a dog in this hunt.  But I do not like seeing people bent over at the cash register wanting to do something that isn't that expensive to do.

[Racerstev]

No one talks about the series- Parallel switch, I was close to trying it. 
 

2 six volt battery’s, they go series to the starter and parallel for everything else. 

[Racerstev]

[Racerstev]

Edited April 22 by Racerstev
Wrong picture

[Ivan_B]

I think the debate about cost, etc, goes on because many people are not DIY-inclined. They are interested in a "kit", that can be just installed without further consideration, and are willing to pay for it. Similar to taxes: for most, it's just standard deduction and you can do it yourself, with minimal research, for free. Yet, it is "easier" for many people to pay someone else to do it for them.

[Plymouthy Adams]

maybe we need two forums, one for the DIY and one for the Pay as you Go crowd......😀  Never seen the logic of coming here for info and ending the thread with pass this along to my mechanic....if they are a mechanic, he/she should already know if not what to do, but at least how to find the info for themselves and not get watered down third party hearsay.  

[BobDeSoto]

Nobody mentioned  8 Volt!

[Sniper]

On 4/22/2024 at 10:27 AM, Ivan_B said:

I think the debate about cost, etc, goes on because many people are not DIY-inclined. They are interested in a "kit", that can be just installed without further consideration, and are willing to pay for it. Similar to taxes: for most, it's just standard deduction and you can do it yourself, with minimal research, for free. Yet, it is "easier" for many people to pay someone else to do it for them.

 

Well, in that case I will put together a kit and charge even more for it, I'll include bulbs, lol.

[Ivan_B]

That's reasonable, it will be interesting how much you would charge for your own time and effort 😋

[Sniper]

Lol