Electrical: Partial 6/12 volt conversion

[MPallock]

Last year when I installed a 700R transmission in my 54 Commander the new starter that came with the trans required 12 volts neg ground. So I did a partial conversion. I am now finding out that was a mistake. The starting system is 12v
neg ground and the cooling fans are also 12v. The rest of the car is 6v neg ground. The 6/12 battery does not seem to hold a charge for a more than a week and I have verified that the new alternator is putting out 13.8volts. I am thinking of converting the rest of the car to 12 volts and put in a big Optima battery like I have in my other classics and be done with it.
Question is the ignition system is a 6 volt Pertronix coil but am still using points so the coil will have to be changed. The lamps will have to be changed and a dropping resistor will have to be put on the radio. The oil gauge does not care and I don't think the amp meter cares as the current will be reduced . Do the fuel and temp gauge have to be changed or will a dropping resistor work on them? What else am I missing? Turn indicator flasher and horns? Also I live near a classic speedometer place that restores old gauges and they can do a 12v conversion. That may be a good option

Thoughts and input is appreciated.

Thanks,

Mark

[SN-60]

Definitely do the rest of the 12 Volt conversion on Your '54 Commander..... You'll never look back!

[55 56 PREZ 4D]

MPallock is asking for specifics. He has already made his mind up as to a change to 12 volt.
He doesn't need a pat on the back, he wants specifics.
SN-60, Give him the specific information he requested. Give of your knowledge. In the past, you have offered your help.
Part numbers, resistor sizes, where and what to purchase, methods. Step by step.
Walk him through it and while your at it please post the specifics on the site to enlighten the rest of us.

[Mike Van Veghten]

MP -

This is what I'll be installing soon for my gauges -

http://vintageautogarage.com/gauge-reducer.html

Small little block, easy to mount, one reducer will work on all of the light amperage draw items (gas, temp gage, clock, etc.).

You need a 12 volt coil, points and condensor don't care what the voltage is.

Mike

[RadioRoy]

The clock is definitely NOT a light amperage draw. Modern quartz clocks draw little current, but a 55 Studebaker clock draws a relatively big current when the winding solenoid kicks in. These reducers are perfect for the temp and gas gauges, but will not work for the clock.

[Tom Bredehoft]

I fried two Runtz units on gas and temp gages in my '55, when I switched to 12 volts. I now have a resistance between the temp sensor and the gage, it reads 180 at actual 160, but I have no idea what the temp is when the gage reads "HOT", it never has moved beyond perhaps 190, still on the gage.

The fuel gage, I purchased a modern 6 volt tank unit, it reads backwards, full it reads 1/8, empty about 7/8ths.

I built (can't duplicate it) a 7 volt source that supposedly puts out 10 amps as needed from 12 volts for my clock.

Best answer, buy 12 volt gages.

[MPallock]

These units seem to be just what I need. I'll install them and let you all know. How it turns out.

Thank you

Mark

[willisl55]

RadioRoy, what do we do to make the clock work correctly after a 6 to 12 volt conversion. I have converted everything but the clock and would really like to have it functional. Thanks, Lee

[gordr]

About the clock? Can I suggest that you feed it from a voltage regulator, such as those described above, but incorporate a resistor and battery in the circuit. Feed unswitched 12 volts to the regulator, take the 6 volts out, pass it through a 20 ohm resistor, and connect it to a small 6 volt gel-cell battery. Feed the clock off that. The gel cell gets a constant float charge from the regulator, and the 20 ohm resistor protects the regulator from the current surge that occurs every minute or so when the points close in the clock. Only downside might be that the regulator itself consumes a little current, so the main 12 volt battery might run down sooner during long storage periods. A battery maintainer would take care of that.

[SN-60]

RadioRoy, what do we do to make the clock work correctly after a 6 to 12 volt conversion. I have converted everything but the clock and would really like to have it functional. Thanks, Lee

That clock will rewind OK with a shot of 6 OR 12 volts!

[RadioRoy]

RadioRoy, what do we do to make the clock work correctly after a 6 to 12 volt conversion. I have converted everything but the clock and would really like to have it functional. Thanks, Lee

Get it converted to a quartz movement. Lots of folks advertise in Hemmings Motor News. It will actually keep time if you convert it.

If CASO is more your leaning, leave the fuse out and ignore the clock.

[Corley]

I'd just stick a resistor in series with the clocks power lead. You may need to measure the resistance of the clock's coil, then use the same value resistor in series. A 1/4 watt resistor will do fine, since the duration of the wind pulse is so short, it will not heat up. (I imagine something like 15 - 20 ohms would do the trick...) JMHO

[gordr]

I'd just stick a resistor in series with the clocks power lead. You may need to measure the resistance of the clock's coil, then use the same value resistor in series. A 1/4 watt resistor will do fine, since the duration of the wind pulse is so short, it will not heat up. (I imagine something like 15 - 20 ohms would do the trick...) JMHO

A resistor probably would work, but I'd use about a 5-watt unit, because the in-rush current to the solenoid can go quite high. Actually, an ignition ballast resistor might be fine for the job. And mount it some place where it can safely dissipate heat, in case the clock contacts stick, which they are wont to do, especially if the battery gets low.

[SN-60]

I'd just stick a resistor in series with the clocks power lead. You may need to measure the resistance of the clock's coil, then use the same value resistor in series. A 1/4 watt resistor will do fine, since the duration of the wind pulse is so short, it will not heat up. (I imagine something like 15 - 20 ohms would do the trick...) JMHO

Not necessary!

[Jerry Forrester]

I'm with SN-60 here. I have never had any problems running a 6 volt clock on 12 volts. I think you guys are overthinking this.