So, I started looking at the Caddy over the weekend and have decided that the electrical system is my #1 concern/priority. The 64 year old wiring is definitely showing its age and just about every piece of it is suspect.
I'm planning to completely replace the harness with a universal type. Even though it was a heavily optioned car for its time, it pretty straightforward by today's standards and the generic "hot rod" set up should work fine. Working with electricity is my day job (industrial controls) and I'm more than comfortable with the task, even without it being designed specifically for my vehicle.
Anyway, I'd like to convert from 6V to 12V at the same time - can anyone think of any reasons to not do so? Obviously, I'll need an alternator, starter solenoid, lights/bulbs, etc. and will probably use step down resistors for some of the specific/hard to replace parts (gauges, wiper motor, etc.) Am I missing anything important?
I did it on my '52 Dodge. Use a GM one wire alternator. Keep the 6V starter solenoid, it spins faster with 12V. No harm ever came to mine in a number of years of driving. If you like the looks of your gages, then go for a step down and keep them.
Not much else to it.
Dan
Yeah. You can't just use a "step down resistor." You'll need to utilize a 6-V voltage regulator unless you know the exact impedance of all of your 6-V accessories and also know that said impedance will never change.
The existing wiring, depending on condition is usually heavier than what is used for 12 v. Of course, I assume you already know that.
It will even help with spinning solenoids.
Sky_Render wrote:
Yeah. You can't just use a "step down resistor." You'll need to utilize a 6-V voltage regulator unless you know the exact impedance of all of your 6-V accessories and also know that said impedance will never change.
I used the term "step down resistor" just because it's easier for most people to understand, but my intention is to use a voltage divider circuit with two equal valued resistors. This will cut voltage in half regardless of impedance. The only trick is to size them appropriately as to not be overloaded.
I intend to do this for the gauges for sure, not sure of other devices yet.
iceracer wrote:
The existing wiring, depending on condition is usually heavier than what is used for 12 v. Of course, I assume you already know that.
Agreed, the wiring is being replaced because it's 64 years old and crusty. The 12V conversion is happening at the same time because it seems appropriate.
How will the hydraulic system cope with double the voltage in the pump and solenoids? 6 volt alternators are a thing, that's the route I would take, if any. If Cadillac, maker of the finest cars available at the time, deemed 6 volts appropriate, I see no reason to change that.
That_Renault_Guy wrote:
Sky_Render wrote:
Yeah. You can't just use a "step down resistor." You'll need to utilize a 6-V voltage regulator unless you know the exact impedance of all of your 6-V accessories and also know that said impedance will never change.
I used the term "step down resistor" just because it's easier for most people to understand, but my intention is to use a voltage divider circuit with two equal valued resistors. This will cut voltage in half regardless of impedance. The only trick is to size them appropriately as to not be overloaded.
I intend to do this for the gauges for sure, not sure of other devices yet.
No, that won't work. Let's say you use two 5-ohm resistors as your voltage divider. Now you've got a total of 10 ohms of resistance, with 6 volts across each of them. Right?
OK, now you take the second resistor and use it as your 6-volt reference. you plug a 5-ohm accessory into this voltage divider. Now the second half of that voltage divider is two 5-ohm resistors in parallel, for a combined resistance of 2.5 ohms. This means your voltage divider is now a 5-ohm resistor and a 2.5-ohm resistor, so you'd have 8 volts across the first resistor and only 4 across the second two in parallel.
You need a voltage regulator and/or a zener diode.
That_Renault_Guy wrote: Anyway, I'd like to convert from 6V to 12V at the same time - can anyone think of any reasons to not do so?
If the charging system works as is, I'd save my money and leave it 6 volts. Unless you're going to drive it in cold weather, or add a stereo or other electrical devices that requires more power, I don't think there's any real advantage other than 12 volt batteries are easier to find.
If you do make the change anyway, consider using a 12V generator instead of an alternator - it will reduce the amount of wiring changes required and it should bolt right in place of the 6V generator, so you dont have to fab up new brackets. My '61 Bonneville is still running its original generator, I put in a new set of brushes and bearings fifteen years ago and it still works just fine.
I think the only advantage of a one wire alternator is it saves you one wire...a standard GM alternator will work just as well, and if it does die for some reason you can pick up a new one at any auto parts store.
Sky_Render wrote:
No, that won't work. Let's say you use two 5-ohm resistors as your voltage divider. Now you've got a total of 10 ohms of resistance, with 6 volts across each of them. Right?
OK, now you take the second resistor and use it as your 6-volt reference. you plug a 5-ohm accessory into this voltage divider. Now the second half of that voltage divider is *two 5-ohm resistors in parallel*, for a combined resistance of 2.5 ohms. This means your voltage divider is now a 5-ohm resistor and a 2.5-ohm resistor, so you'd have 8 volts across the first resistor and only 4 across the second two in parallel.
You need a voltage regulator and/or a zener diode.
Skyrender - You are totally, 100% correct and I am totally, 100% incorrect. Thanks.
Shouldn't this board have an embarrassed or headsmack emoticon? 
