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WORKING THREAD: 12v conversion for a '47

Started by Justin Norwood, February 20, 2018, 07:17:53 PM

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Justin Norwood

Context:
I am converting my 1947 Series 62 Sedan from 6v to 12v (I need AC), while simultaneously switching to Pertronix electronic ignition (my points-style unit just died). I am using a CS121 alternator w/ internal voltage regulation.

I recently completed my parts list, with help from the gurus on this forum (Thanks!!!). This thread is going to be my working thread for questions that I have along the way. Hopefully this won't take long.

Question #1: Since my ALT is internally regulated, I know that I need to 'delete' my external voltage regulator on the firewall. Can someone please suggest the best way to do that? Do I simply unplug the three wires and tape them off, or do I need to jump some of the wires to complete the circuit?
1947 Cadillac Series 62 Sedan

bcroe

In my opinion its good to remove all the wiring associated with the
old generator and mechanical regulator, and replace them with the
2 or 3 wires required to support the internally regulated alternator. 
And a 12V dash bulb is supposed to connect from one of those wires
to an IGN circuit, its purpose is to quickly start the alt or indicate a
failure. 

Some others may find a way to jumper out the original wires with
a fake regulator, and hide the bulb.  Bruce Roe

Bobby B

Justin,
Hi.. If you follow your wiring diagram, You'll see which wires need to connect internally. I gutted mine and used it as a "Splice Box" so it looks factory from the outside. You can drill a mini self-contained 12V Red "pilot" light ( available at an electronics store or electrical supply house) anywhere you want. Usually the diameter of a pencil eraser. Good Luck!
                                                         Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

Justin Norwood

Thanks Bruce & Bobby. I just ordered the pilot light -- the gentleman at the alternator shop said the same thing! ;)

QUESTION #2: Where does the 12v to 6v voltage regulator for the gauges get inserted? I assume it should be just "upstream" of the Ammeter...but I want to be sure.

P.S. Forgive my dumb questions for the moment -- I am operating without the benefit of a 1947 wiring diagram at the moment. I ordered one last night.
1947 Cadillac Series 62 Sedan

Justin Norwood

#4
Good news: I found a wiring diagram for my car online! (see attached)
Bad news: I still need help with question #2 above.

As it relates to where I should place the 12v to 6v VREG, I put a red circle on where I was proposing to insert it on the wiring diagram. That said, if I am reading that right, doing so would drop the voltage to 6v not only for all of the gauges, but also for the igntion switch (and by default, the ignition itself), as well as all of the exterior lights (headlights, brake lights, license plate lights, etc). That can't be right...  Your advice is greatly appreciated!
-Justin

1947 Cadillac Series 62 Sedan

Justin Norwood

#5
thinking about the bigger picture for a moment...
perhaps my issue/challenge is that I went into this 12v conversion thinking that it was a simple job, not requiring much thought...simply "swap your battery and ALT, and drop in a VREG for your gauges." ...but in reality I am realizing that I am going to have to 'get my hands dirty' (mentally speaking) and map out a new wiring diagram from a clean sheet of paper, then try to retrofit that to the existing diagram -- using existing wires where possible. Am I getting a better sense of this job now?

Assuming so, I've started to create a list of what components should be on a 12v circuit and which ones should be on a 6v circuit. Could you please take a look at this chart and tell me if I got anything wrong?

12 VOLTS
~~~~~~
Battery + Alternator
Starter + Starter Solenoid
Ignition Switch, Ignition switch lamp, Starter button, Ignition coil, Distributor, Spark plugs
All external lights + interior dome light + trunk light + associated switches (e.g. headlight switch, fog light switch, turn signal switch, dome light switch, etc)
Horn (I have a 12v relay)
Heater motors (I am upgrading to 12v motors)
Cigar lighter (I am going to convert this to a USB charger)

6 VOLTS
~~~~~~
Ammeter gauge
Gas gauge
Temp gauge
Instrument lights (e.g. Speedometer light, Headlight beam indicator light, turn signal indicator light)

NOT SURE
~~~~~~~
Hydramatic neutral/position sensor?
Engine temp sensor?
Fuel level sensor?

NOT APPLICABLE
~~~~~~~~~~~
Clock - I will deal with that later; probably 6v
Radio - I am probably going to unplug the radio, but leave it there for asthetics


Does this sound right???
1947 Cadillac Series 62 Sedan

bcroe

#6
Quote from: revvies
thinking about the bigger picture for a moment...
perhaps my issue/challenge is that I went into this 12v conversion thinking that it was a simple job, not requiring much thought...simply "swap your battery and ALT, and drop in a VREG for your gauges." ...but in reality I am realizing that I am going to have to 'get my hands dirty' (mentally speaking) and map out a new wiring diagram from a clean sheet of paper, then try to retrofit that to the existing diagram -- using existing wires where possible. Am I getting a better sense of this job now?

Assuming so, I've started to create a list of what components should be on a 12v circuit and which ones should be on a 6v circuit. Could you please take a look at this chart and tell me if I got anything wrong?

12 VOLTS
~~~~~~

6 VOLTS
~~~~~~
Ammeter gauge
Instrument lights (e.g. Speedometer light, Headlight beam
indicator light, turn signal indicator light)
Fuel level sensor?

Does this sound right???

Now you have it.  Your ammeter will remain in the main power
now at 12V, it is sensitive to current, not voltage.  I would expect
supplying 6V to your other gauges, which includes the fuel level. 
I would try to convert ALL lights to 12V, unless the instrument light
circuit cannot be segregated from the gauges. 

I might attempt this with a drawing for each modification area,
that goes with your original main drawing.  These would show
exactly how each change is made, disconnects and new connections. 

good luck, Bruce Roe

35-709

I had no trouble finding the correct instrument bulbs in 12 volts for my '35.

Bulbtown
is just one of several specialty bulb houses on the internet --- www.bulbtown.com

Do a Google search for antique and classic automotive bulbs  call whichever one you choose and ask for the 12 volt equivalent of the 6 volt bulb you want to replace, or search their site.
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible - Sold
1950 Packard 2dr. Club Sedan
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2