12V conversion usefull on a beaten 36 Sedan?

[sjaakslinger]

We're trying to get a plan together on how to get our 1936 Touring Sedan back on the road after sitting for probably 55 years.

One issue is the electrical system. It still has the (working) 6v stock alternator (or generator?) with positive ground and later added turn signals lights. We're not planning anything extra here, probably keeping it all stock. We'll replace all the wiring, either reproduction harnesses or Painless Wiring (or similar). Any advice in that is welcome as well btw.

Since the car will 'only' get a technical rebuild (frame, brakes, engine and electrical), the used look of the car will remain, inside and outside. So we're doing this kinda on a budget. What are the recommendations here? 36 has the alternator pulley mounted fan, so I guess a 12V alternator is pretty specific?

Thanks.

Dennis

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[GB SISSON]

I will add my two cents. Based on what you have told us I think you should keep it 6v. Make sure your battery cables are of large diameter and terminals are very clean and tight. Clean all the ground contacts as you rework the wiring and when in doubt, add a few ground cables between body and frame, frame and engine, anywhere tucked away. You'll be fine with the six volts, but if you insist, your original generator should be converted to 12 v. I know it's done with starters. Oh, and don't wash it as that will just lead to endless fixing and fussing and worse.

[tubman]

I would think this decision may depend on the availability of decent 6 volt batteries. It's tough enough to get an Optima here in the states. What's going on overseas is a complete mystery to me.

[38 coupe]

If you go 6V you should use a reproduction stock type wiring harness. Some of the reproduction harness places will add the wires for turn signals when making the harness if you ask before ordering. The wires for 6V are larger than 12V since lower volts draws more amps.

[Brian]

Your existing 6 volt, 3 brush generator will indeed charge a 12 volt battery. Change out the 6 volt cut out [that round thing on top of generator] , for a 12 volt cutout, or install a diode in the original cutout housing. Polarise the generator for neg earth, adjust the third brush and you're racing....

[5851a]

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As 38 coupe suggested, an original type harness. Any of the generic harnesses like painless are based off of GM products. JMO I did one vehicle for a person and the harness was about as far away from a painless installation as you could get. Owner supplied.

[sjaakslinger]

Thanks for the input everyone. What would be the pros and cons for both 6V and 12v (and changeover to negative ground)?

How's the availability of 6V light bulbs for example? LEDs maybe?

Dennis

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[drolston]

Both 6v and 12v bulbs are available for every bulb on that car. For safety reasons, I would recommend replacing all wiring with a harness designed for 6v, including the turn signal. You can decide on whether you want to convert to 12v after you have lived with it for a while. Again for safety I would consider replacing the headlights with sealed beam bulbs. They are available in both 6 and 12 volts.



Give the steering and front suspension a good going over. More than +/- 2" play at the steering wheel rim probably means you need new tie rod and drag link ends. Look at those while someone moves the wheel back and forth to see where the slack is. If not the rod ends, it could be the steering box needs adjustment (easy) or a rebuild (not easy). Jack up the front end and try to jiggle the wheels holding the top and bottom. Any perceptible looseness there means king pin bushings. Not easy but not too big a deal.



Has the car been upgraded to hydraulic brakes, or does it still have the mechanical brake rods? I would convert to hydraulic, using the Lincoln or Bendix self-energizing brakes. I did my '35 60 years ago and it is pretty straightforward. For the speed (or lack thereof) that you will be driving, mechanical brakes are fine. IF they are properly maintained. You will probably need to replace every clevis in the system; not a big deal. And maybe some of the springs.



Please report progress with some photos!

[paul2748]

Most aftermarket harnesses (not reproductions) are designed for 12V and are not safe with 6 V because of the amperage draw. If going to an aftermarket harness and keeping the car 6V ask the seller/manufacturer if safe for 6V.


You should be ok with a reproduction harness if staying with 6V but again, check with the seller/manufacturer.

[terry]

Originally Posted by Brian

Your existing 6 volt, 3 brush generator will indeed charge a 12 volt battery. Change out the 6 volt cut out [that round thing on top of generator] , for a 12 volt cutout, or install a diode in the original cutout housing. Polarise the generator for neg earth, adjust the third brush and you're racing....

What Brian says is true but the 3 brush generator will overheat if you're not careful. Amperage output should be controlled to not go over 9 or 10 amps if I remember right. I have an unused 12v neg regulator that looks just like the original 6 volt cutouts and sits right on top of the generator if you're interested. terry

[SoCalCoupe]

Originally Posted by GB SISSON

I will add my two cents. Based on what you have told us I think you should keep it 6v. Make sure your battery cables are of large diameter and terminals are very clean and tight. Clean all the ground contacts as you rework the wiring and when in doubt, add a few ground cables between body and frame, frame and engine, anywhere tucked away. You'll be fine with the six volts...

Agree. Had big plans for lots of conversions when I got my car 18 months ago, including a 12V. Best advice I got was take it slow. I've ended up doing very few modifications. Kept it 6v. Chased down some regulator and ground issues and now it's VERY reliable.

Originally Posted by tubman

I would think this decision may depend on the availability of decent 6 volt batteries. It's tough enough to get an Optima here in the states. What's going on overseas is a complete mystery to me.

Originally Posted by sjaakslinger

Thanks for the input everyone. What would be the pros and cons for both 6V and 12v (and changeover to negative ground)?

How's the availability of 6V light bulbs for example? LEDs maybe?

Keeping it 6v PROS:
- no conversion cost (could be up to $500 U.S.)
- no second and 3rd order effects of change one thing, now you have to change this, then this, etc.
- engineering is already done. You don't have to figure out how to make a one-off non-stock situation work, especially when it breaks
- you can find 6V LED's for everything
- when it comes time to replace parts, you can use stock parts

Keeping it 6v CONS:
- harder to install a rolling thunder dome 24 speaker stereo with a seismic wave subwoofer
- probably can't add A/C
- might be harder to find a battery

[ronn]

you mention, on a budget


well the correct harness is going to be around 500.00............

[ssffnomad]

6V or 12V may not be the first question that needs to be answered .

Question #1. What is the overall condition of the original Harness ?
If it’s a typical 80+ y/o Cloth frayed harness.
Please give her a new Harness.

[sjaakslinger]

Thanks again for all the input.

@drolston
The car still has the original mechanical brakes. Seems to be all complete and working. If we keep them, we'll of course go over the entire system. Most probably add those floaters that are available from Flathead Ted. We're not so sure on converting to hydraulic brakes yet, being limited to what's available here in Europe.

@paul2748
I was already looking at the repro harnesses that are available through the different vendors. Those which are reproduced after the originals. I didn't see any voltage specs so far, if I go that route I'd have to check with the vendors.

@SoCalCoupe
No need for A/C, more need for heating actually.[emoji16] No need for a sound sytem either. Batteries, not so sure. I think there are available, betting there's a mraket here for those as well.

@ronn
Well, on a budget as far as feasible. Some things just need to be addressed correctly.

The original harness is toast. Completely. Except for the later installed turn signals. So we have to completely replace it.

Here are some more pics btw.

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[Flathead Fever]

I vote to keep it the original 6V positive ground. It definitely needs a new harness. The car obviouslky operets just fione on 6V when it was new.

The advantage of 12V is it will crank faster and have brighter lights. They make 12V alternators that kind of look like the original generators. Powermaster is making them now with bearings that can support the fan mount. For years they recommended not using a fan on those aftermarket 12V alternators that look like generators. They are expensive, over $700.00 That would be the most expensive part of a 12V conversion. 6V batteries are getting a little hard to get, which would be one reason to switch 12V. It took me about months to get a 6V Optima battery for a Model A.

[SoCalCoupe]

Originally Posted by paul2748

Most aftermarket harnesses (not reproductions) are designed for 12V and are not safe with 6 V because of the amperage draw. If going to an aftermarket harness and keeping the car 6V ask the seller/manufacturer if safe for 6V.

You should be ok with a reproduction harness if staying with 6V but again, check with the seller/manufacturer.

Just can't stop talking about this. Totally agree. A 6V harness should work fine with a 12V conversion but the opposite is not true. A 12V harness may be unsafe in a 6V car. Current (i) = Voltage (V) / Resistance (R). Power = I squared R.



The story I've heard is that the reason for converting the industry from 6V to 12V was to reduce the cost of wiring harnesses by reducing the amount of copper. Wire can only take so much current before it fails. To increase the amount of power a wire can carry without failing you have to increase the voltage and reduce the resistance of the loads. It's easy to increase the voltage, very hard to reduce the resistance. There are some costly physical barriers to reducing resistance; much easier to increase voltage.


So, by re-engineering the loads (R) and increasing voltage (V) you can transmit the same power over smaller wire.


If you put a 12V harness into your car and then convert to 6V, there may be too much current in the wire to be safe.

Originally Posted by Flathead Fever

I vote to keep it the original 6V positive ground. It definitely needs a new harness. The car obviously worked just fine on 6V when it was new.

The advantage of 12V is it will crank faster and have brighter lights....

I'm on the same page with Flathead Fever and all the other 6Vguys.


Yes, the starter runs faster on 12V than 6V but if the starter in an original car isn't running fast enough at 6V to start the car, then there's some other problem: possibly ground, starter, ignition or carburetor.



I was in this boat too, so I get it. My 6V car would not start hot or at least with great difficulty (extremely slow cranking.) Finally figured out that the engine ground was defective. Fixed it for minimal expense. Now starts great when hot. Could have been one of the other issues.



Sorry for rambling. 6V is one of my pet topics.