6 volt to 12 Volt conversion

[steve fritz]

I am converting my 55 Ford to 12 volts. I will be changing to 12 volt starter, gen , regulator , and heater blower motor, using these from a 56 Ford.
My question is on the sending units for oil and water temp. Do I need to change these out as well to the 12 Volt units. I will be using the voltage step down unit and keeping the 55 dash cluster water temp and gas gages.
Thanks for any input.
Steve

[miker98038]

The oil sender is an idiot light, isn’t it, so it doesn’t care. Change the bulb to 12v. Or, leave it if it’s on the 6volt drop resistor. The water temp needs to see only 6 volts, as does the gas gauge. The 56 units are 12 volts (at least in a ‘bird) and I think the only year in that time frame that didn’t use a drop resistor to 6.

There’s been some discussions of different drop resistors here, either do a search or wait for someone who knows to chime in. I don’t remember the detail, but some apparently don’t work well with the King Seeley (?) gauges.

[dmsfrr]

According to this (T-bird) link you do not need to change original King-Seeley style Temp and Fuel gauges or sending units as long as they are original working matched pairs.
https://www.ctci.org/battery-for-6v-to-12v-conversion/
They are not voltage or polarity sensitive and self-regulate based on current & heat not voltage. (diagram 1 below)

If you change them you'll need oem 6v or aftermarket 12v gauge & sender matched pair replacements.
The oem '55 gauges will (usually) not work correctly with '56 or aftermarket senders.

miker98038 is correct about the oil pressure idiot light, just change the bulb.

You don't need to change the 6v starter unless you intend to really grind on it for a long time.
It will spin the engine faster and it may start easier.

You will need a 4 terminal 12v starter solenoid if you're using stock points and a ballast resistor.
The ignition coil is polarity sensitive (Before/After diagrams 2 & 3 below)
...and the clock too, if it has one.

Quote from the link above...
"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 it’s position on the voltage regulator." diagram 4

[scicala]

Steve, I converted a '52 Ford to 12 volts and just used the Ford factory voltage reducer (regulator). I'm pretty sure I gave you one with the car. About 2" long and 3/4" wide with two terminals.
It needs to go between the ignition switch and the back of the cluster to one of the gages. If you look at the shop manual schematic it should show the wire going from the ignition switch to the back of the gage panel.


Sal

[steve fritz]

dmsffr.....thanks for the reminder about the ballast resister , I will be sure to add that.
On that fuel tank sender....CARPENTER has a tank sending unit they claim works on 6 or 12 volt , I wonder if it will work with my stock 55 dash gage? CARPENTER is usually pretty reliable on the stuff he sells. Anybody else tried that sending unit with the stock 55 dash gage???

[miker98038]

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I wish I would have known that about the gauges when I went to 12 volts. I replaced the works with 56 units. On the other hand, my gauges were pretty faded. My 6 volt seat motors, window motors and horn have been fine, but I don’t abuse them. The heater I changed, continuous use kind of scares me.

[dmsfrr]

Originally Posted by steve fritz

dmsffr.....thanks for the reminder about the ballast resister
...
On that fuel tank sender....CARPENTER has a tank sending unit they claim works on 6 or 12 volt , I wonder if it will work with my stock 55 dash gage? CARPENTER is usually pretty reliable on the stuff he sells.

You're welcome.

Because the old King/Seeley gauges don't electrically function the same way as newer repro senders the odds aren't the best.

It's possible that it might work correctly across the whole Full / Empty scale, or not. You could need to buy a sender-matching reproduction gauge from them, or find a good oem '55 fuel sender instead.
Is the '55 fuel tank sending unit you have missing or in bad shape? Sometimes they can be repaired.

[steve fritz]

The 55 fuel sending unit is pretty bad , I'll take a closer look at it tomorrow.

[miker98038]

I’ve had good luck with Classic, but check the last comment.

https://www.classictbird.com/Fuel-Se...uctinfo/9275A/

[Daves55Sedan]

The '55 temp sending unit (6-volts) looks identical to the '56 unit (12-volts) and fits in the same pipe thread.
If you decide to change to all '56 sending units and matching '56 gauges, that is the only year that the systems used full and un-regulated 12-volts. Replacement '56, 12-volt temp sending units are still available at many of the repro parts suppliers, but they are pricey. You can remove the faceplates and needles (carefully) from the '56 gauges and swap in your old '55 faceplates and needles onto the '56 gauges.
If your Y-block heads are off of a '57 or later year, the sending unit is a different pipe size and you may have some trouble. The '57 and later instrument systems utilized a regulator (which can also be purchased new), but you need to use a '57 guage. Same faceplate and needle swap is needed.
You can get around doing all that by pulling out the threaded bushing in the head and installing a new bushing with the smaller pipe thread (also available from repro parts suppliers). Then you can use the '56 temp sender and '56 guage without regulator.

[50fordcoupeman]

My car is 12v. The heater motor is 6v and has worked fine now for 4 yrs. The wires and motor itself does not get hotter than normal. Might give it a try before you change it out.