Ramblin Reck
Senior Member
I want to...."Change 12V Positive Ground to Negative ground" on 39 Ford.
What do I need to do and or change out?
What do I need to do and or change out?
Change 12V Positive Ground to Negative ground
- Thread starter Ramblin Reck
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Ramblin Reck
Senior Member
Will an administrator remove my duplicate posting? Thanks Sorry
Brian
Well-known member
Ahhh, I don't know which duplicate posting you want removed..As I said in reply to your other post, simply reverse ammeter connections, reverse battery connections, polarise the generator by flashing the field wire momentarily to the A connection on the regulator, reconnect the field wire to regular F terminal, drive off...
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Ramblin Reck
Senior Member
The Duplicate post has NOT been deleted.
How and where do I reverse Ammeter connections? I assume the Ammeter is the one inside the Speedometer and reads voltage?
I got Reverse Battery Connection. Connect Negative terminal to chassis and positive to Coil or whatever the Negative Terminal is presently connected to.
Polarizing the Generator has me a little confused. The field wire is found where? The "A" connection on the regulator is identified by what? The Regular "F" Terminal is found where? Maybe if I took the cover off of the regulator which I assume is the "voltage regulator" attached to the fire wall and says 12V on it, I would be more enlightened and knowledgeable about that of which you speak.
Change all Light Bulbs? A light bulb has no polarity is my understanding. Also all headlights, brake lights are already 12V, as is the battery and all work fine right now. There may be a 6V light bulb in the Speedometer which may need to be changed.
I will appreciate any and all advice since this is kid who almost burned his grandmother's house down 70 years ago trying to fix a nonworking light socket in a house built in the 19th century. That's why they call me Sparky! "I ain't doing this" until I feel 100% sure that I understand what and why I am doing it and the proper sequence of changes. Not that your instructions aren't crystal clear to an expert auto mechanic.
I may still have to use a Runtz resistor in line with the individual oil pressure gauge and other 6V meters? I don't begin to know how and where to connect these resistors. Also I had heard that there exists another resistor that requires only one resistor for all 6V systems rather than one for each device. Anybody know the brand if it exists?
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rotorwrench
Well-known member
What I'd like to know is why the system was set up with positive ground in the first place. This is not common on US cars with 12-volt systems. Does the system have an alternator or a generator that's making the 14-volts required? If it's a generator, what type is it? We need to know this stuff to give an accurate reply to the question.
Cadillac_chris
Junior Member
Coil bullbs and use a step down on any 6v gauge that requires power is all I’ve ever done as well as charging system
Ramblin Reck
Senior Member
According to a friend, it is a Generator because it is long and black, not short like an alternator. No label on it. No way to question the former owner as to "Why" He gone.
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itslow
Well-known member
He's using the shape to determine if it's a generator or an alternator, which is a relatively reasonable thing to do unless it's one of the Powermaster units.
rotorwrench
Well-known member
The power master is likely a one wire alternator made to look like a generator. A generator may be an early 3-brush type that uses a cut out mounted on top or a later 2-brush type unit that has an external regulator somewhere. The late type generator will have a field terminal and ground terminal on the side and an armature terminal on the back side for a 3-wire hook up. It just depends on whether it is in fact a 12-volt converted generator or a 1956 and later generator made to fit an early application. 1956 was the first year Ford started to use 12-volts in the V8 era. They were all negative ground. 6 and 12-volt 2-brush generators all used a 3-pole voltage regulator that is generally mounted to the firewall. If there is no voltage regulator and no cut out then it may be a power master alternator that looks like a generator. There are also other generator to alternator conversions out there but I don't know how many.
From the model A era through 1955 Ford used the 6-volt positive ground systems. Model T cars had various systems so I won't mention them here since it doesn't apply.
From the model A era through 1955 Ford used the 6-volt positive ground systems. Model T cars had various systems so I won't mention them here since it doesn't apply.
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JSeery
Member Emeritus
In your case I think it would be much easier to use the voltage reducer Ford used when they switched to 12 volts. It drops the voltage to all the gauges with just the one unit and connects between the power wire going to the gauges and the connection on the gauge unit. This units were used for a lot of years up into the 1980s, a 60s era mustang unit is commonly used. The only real difference between the different years is the type of connecters they use for the wires.
Here is a C & G reference, but any auto supply shop should have them: https://cgfordparts.com/ufolder/fordpart.php?number=C6DZ-10804-A
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Ramblin Reck
Senior Member
There is a 12Volt regulator bolted to the firewall. I see two wires coming off of the back end of the generator. One goes to the coil. The other is inside of a wire harness and I assume goes to voltage regulator. Looks like same markings on wire connected to Regulator as the one coming off of the Generator. Attached are two wire coming off of backside of the Genny. Should there be a third wire that I just haven't located yet? There is another picture of the 12Volt Regulator bolted to the Firewall.
Additionally, can you identify what looks like a pressurized container bolted on the firewall at about 11 O'clock from the voltage Regulator? Thanks I need all the help I can get to understand this situation. I may just leave as is and buy the 12 to 6 volt reducer from Vintage Auto.
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Ramblin Reck
Senior Member
Ramblin Reck
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Ramblin Reck
Senior Member
That is definitely a picture what is attached to the firewall. Perhaps it was part of the original Flathead because the original Flathead was replaced with a 1946-1947 Flathead. Thanks Believe you solved that mystery.