12 V conversion


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By Rowen - 7 Years Ago
Will 55 signal and headlight switches work on 12 V? If not, will 56 switches work? Thanks
By oldcarmark - 7 Years Ago
.The Signal Switch will work no Problem. The Headlight Switch has that "Rheostat" to dim the Dashboard Lights. You will have to move the output Wire to a Terminal on the Switch that is live with Switch pulled to turn on. U  won't be able to adjust the Brightness. It will be on full Bright. The Rheostat is an adjustable Resistor and You need to bypass it. I remember doing that Years ago when I changed my '53 to 12 Volt.You will need to step down the Voltage to Gauges. You may  need to ad a Ballast Resistor depending on what Coil U use. Also change the Solenoid to the 12 Volt One with 2 Small Terminals. Run a start bypass Wire from the "I" Terminal to + side of Coil. You do need to change the Signal Flasher to 12 Volt Unit as well.
By Rowen - 7 Years Ago
Thanks mark. The dash light thing won't be so bad. I don't do a lot of night driving so I will use the stock switch. I am VERY happy to hear the signal switch is good to go. As far as the gauges go that won't be a problem either. I will have gauges inside for oil, temp, fuel, and amp. There will also be a tach
By Rowen - 7 Years Ago
Has anyone here ever used an "original" 6v alternator bracket to mount a 12v one? Is there a specific alternator that will fit and work in this bracket? No pics of it but can get some if needed. I realize it is NOT original equipment. it was on the car when purchased so has been on the car 40+ yrs. Thanks for any help on this.
By Florida_Phil - 7 Years Ago
I research this when I first purchased my 55 TBird about 6 months ago. As it turned out my car had already been converted to 12 volts which I didn't realize.  My car had a 12 volt battery, but the ground was positive.  I reversed the cables, repolarized my voltage regulator and it has worked ever since.  I believe my car still has the 6 volt starter and I haven't had a problem so far.  All my gauges work.  My radio had been converted to a positive ground and I'm afraid to hook it up.  I also have the clock disconnected for the same reason.  There are dozens on articles on the Internet about these conversions.  Here is the text from the one that I found the most helpful.  It came from the H.A.M.B. website.  I hope I am not breaking any rules by posting it here.

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Some of you are making way too big a deal of the 6 volt to 12 volt conversion on the 55 Thunderbird. For instance, you don't, or should not need a wiring diagram. You don't need to rewire the car. All the wire for the 6 volt system is twice as large as need be for 12 volt service. The only thing you need to change under the dash is the dash light bulbs and maybe the cigar lighter if you still smoke. The polarity for the clock must be changed from positive to negative ground. You may need to remove the clock to do this. There is a little tab that is designed to be positioned for positive or negative ground. Position it for negative ground. Major damage will occur if it is powered up in reverse polarity. You must install a 125 ohm 10 watt resistor in series with the 6 volt clock to drop the voltage to 6 or 7 volts.  Of course the radio will need to be replaced, converted to 12 volt, or powered through a voltage dropping resistor. It is not polarity sensitive. You do not need to change any switches or gauges on the dash. The fuel and temp gauges will work on 6 or 12 volt and are not polarity sensitive. If you miss some of the dash lamps you can change them after they burn out, make sure you put in 12 volt lamps. The direction lamp flasher must also be changed for best performance but you can change it later. The fuses may need to be changed to values smaller to the ones rated for the 56 or 57 Thunderbirds. The tail lamps, the back-up lamps and license plate lamp will need to be replaced with 12 volt lamps. Now for the firewall forward: You do not need to change the battery cables, the horns, the horn relay or the starter. If converting to a generator install a 12 volt one and a 12 volt, 30 amp voltage regulator and wire it up exactly as the 6 volt ones. Or do the alternator conversion. This is done same as a 12 volt generator to alternator conversion. You will need to install 12V head lamps and park and direction lamps. No changes in lamp wiring or the light switch is necessary, leave it alone or repair it as necessary. Of course you will need a 12 volt battery; there are 12 volt batteries that will fit the 55 battery carrier with little or no modifications. The Motorcraft BTX-56 fits nicely and has 550 cold cranking amps. Just make sure to connect the battery to negative ground. The 6 volt coil can be used but the polarity must be changed, just switch the battery and distributor wires or install a 12 volt coil same as used on 56 through 73 Fords or get good used ones from salvage yards. The ones used on the 60 through 64 Falcons are good to use, they have yellow tops. Now for that very minor wiring change that has everyone confused. Install a 12 volt starter solenoid such as the ones used on the 56 through 73 Ford products. They are still cheap at AutoZone. It will have the extra “I” terminal, “I” as in ignition. Run a wire from the “I” terminal of the 12 volt starter solenoid to the battery terminal of the coil, remove the ignition wire that is presently attached to the coil and add a new wire about a foot long to the battery terminal before securing the nut. Now connect both the new wire attached to the battery terminal of the coil and the original ignition wire from the ignition switch to a new ignition resistor, Mororcraft #DY-35.   When the job is done, before you start the engine, remove the field wire from the voltage regulator and strike it (draw an arc) to the battery terminal of the voltage regulator in order to properly polarize the generator then reconnect the field wire to its  proper position on the voltage regulator.  The heater blower motor, the seat motors and window motors will work on 12 volts but they will run very fast. The seat motor running too fast should be no problem. The heater motor running on low speed will be acceptable. Do not hook up the high speed wire so you do not inadvertently run the motor on high as it will burn out the motor. The window motors will require some expertise in use in order to prevent mechanical damage. If you want, you can install 12 volt window motors, but it is not required and they are expensive. You might try using a dropping resistor in the motor ground wire circuit to drop the voltage but I have not determined what the correct value would have to be. It will have to be a very high power resistor, maybe 1000 watts and it will give off some heat. I would recommend just using the window motors as they are and release the window switch before the window gets to its stops. This may take some practice but it is easy enough and like I said before, it will take some practice and finesse. When making a 6 V to 12 V conversions on a 1955 Thunderbird it is difficult to find a battery that fits the 1955 tray and hold down without modifications I have found that a Group 56 12V battery fits the tray and allows the hold down to be used without modification. The length of the battery is slightly shorter but covers well without showing. In fact it looks like it was made for the tray and hold down.   Reprinted with permission from Gil Baumgartner            
       
Footnote: If the 6 volt gauges do not work when the 12 volt conversion is made install a 10 ohm 10 watt wire wound resistor between the gauges and the power supply to gauges. If the gauges still do not work it may be necessary to replace the gauges and the sending units with 1956 12 volt units. Wire wound resistors can be purchased at Radio Shack.
By Rowen - 7 Years Ago
Yes sir. All of that has either been changed over or replaced. I ask about the bracket because I need to know if I can use the alternator bracket I have or if I need to spend the $120 for an aftermarket (speedway) bracket. I will get the bracket and 6v alternator out and see if I can find one that will fit. Thanks for the response.
By charliemccraney - 7 Years Ago
Just for clarification, you currently have a 6v alternator and not a 6v generator?

If you do splurge for a new bracket and are willing to spend that kind of money, get Mummert's cast bracket.  It will be much nicer and you support a guy who caters directly to the Y-Block community.
By Rowen - 7 Years Ago
Charlie, yes sir, came with an altornator. Externally regulated. That's why I started the process of going through the car and converting it. It craped out on me and through what research I was able to find, it was better to put the money into the conversion since I had planned on doing this summer anyway. At least this way I'll be driving it this summer instead of working on it. ......hopefully.....
By charliemccraney - 7 Years Ago
Google alternator dimensions and look at the picture results for dimensions of many common alternators to see if one might work.

If modern alternators don't seem like they will work easily, you might do something like this:
http://www.y-block.info/tips/alt/brack08.jpg
By Rowen - 7 Years Ago
Thanks Charlie, I just took another look at Johns bracket and I will give him a call. It does look nice and as you said, "guaranteed fit".
By charliemccraney - 7 Years Ago
It is a good bracket.  I'm using one of the first ones he produced.
By Rowen - 7 Years Ago
Done, one is on the way. It will fit right in with the cast manifold and valve covers! That was an excellent suggestion. Now if I can only wade through the 50 or so different "Delco one wire" alternators listed on the web, I'll be doing well....they range from $40-$240.....any suggestions? (Please don't say the $240 one...) :0)
By paul2748 - 7 Years Ago
Personally, I wouldn't go with a one wire because you can't get them at your local parts store.
By charliemccraney - 7 Years Ago
I don't have a part number but I have been using a Powermaster 100 amp 1-wire since I installed that bracket.  I don't think it was over $100 but it was probably 7 years ago.  You probably do not need 100 amps.  I have that because I do plan to add more electrical stuff.

Some things to be aware of with any 1-wire is that the post for connecting the wire may be very close to the dipstick tube, as the alternator is supplied.  That's not a problem because you can clock the alternator to move the post to one of 4 positions.  If you don't know how to do that, google clocking an alternator.  For a quick rundown, you remove the 4 case screws, separate the halves just enough that you can rotate the back half to the position you want and reinstall the screws.  Sometimes it's not quite that easy, so google before you start.

Another thing is that the pulley will probably be too large.  You will need the alternator to be turning at a bare minimum of 1800rpm at idle.  For a stock Y, that requires a pulley of about 2.200" diameter or smaller.  For a modified Y with a stock damper and about 800rpm idle, about 2.940" diameter will provide the same alternator speed.  If it is a modified Y and you plan to race, then some compromise may have to be made to ensure an adequate idle rpm while keeping the upper limit below 18000rpm.  For instance, the 2.200" pulley will be fine for either engine at idle but say the modified one is shifted at 6500rpm, that puts the alternator at about 19550rpm.

There are also potential drawbacks to a 1-wire, like remote voltage sensing and having to rev the engine when the engine is started to get the alternator started.  Google that as well.
I have not experienced any of those drawbacks. It's possible that it is outdated info and no longer relevant.  It could be that my electrical system does not currently require enough  to be an issue.  It could be something else but for whatever reason, I do not experience it.  For perspective, I have an electric fuel pump and much hotter ignition than stock on top of the stock stuff and with lights, wipers, heater all going at once, there has never been a problem.
By mrmike - 7 Years Ago
I didn't see any mention of reversing the generator wire thru the generator gauge loop for it to work with the conversion.
By Rowen - 7 Years Ago
Good morning gents, something I should have done when ordering and will do today is just ask John if he has a recommendation. I would like to have it here when his bracket arrives. Thanks for all the responses once again.
By miker - 7 Years Ago
Charlie mentions some 1 wire drawbacks above. I’ve experienced all of those one time or another. Having to put some rev’s on the motor to start charging isn’t a big deal, but delivering low voltage to the battery is. I prefer to hook up the “Gen”light, or whatever is required to start the charging, and the voltage sensing wire from the alternator to the battery. I also like to see full charging voltage, typically 14.4 or so, on the battery at fast idle. Check the slow idle voltage, and full load voltage also. Full load isn’t such a big deal as running the heater on high and the high beams on isn’t something we do much on our older car. But it’s nice to know you’re close to 12 volts even if it drops off a bit.