The Ford Barn

rotorwrench · 11-30-2019, 10:32 AM

The math looks close enough for me per Ohms law.

For Ranchero50
The resistor wires were used by all the big 3 and probably others too. The heat was dissipated over the length of the resistor wire so it wasn't all in one spot. I'm not sure what the coil specs were for those systems either. The mounted ballast is usually 1.3 to 1.5 Ohms and are easy to work with for a 1.5 Ohm coil. I prefer to use the components I know for building a system from scratch. On a GM engine, I'd use an HEI type system with 12-volt. On a Ford engine, I'd use what ever came with that engine unless it has an old Load-O-Matic. Those systems were tied to the carburetor and don't work well without the original carb. The type of vacuum advance signal also has to be considered. Many conventional breaker types can be changed to electronic systems if a person doesn't want points & condenser.

A person always has to keep in mind that a 6-volt system runs at around 7.1 to 7.6-volts in operation. The 12-volt systems are closer to 14-volts in operation with the generator or alternator on line.

Purdy Swoft · 11-30-2019, 04:18 PM

If the ignition switch is left on without the engine running , if the points are closed the coil will get hot whether a resistor is used or not . When a resistor is used with a six volt 1.5 ohm coil , the resistor prevents full voltage from entering the coil . If full 12 volt voltage was connected to a six volt coil it would burn out the coil unless it had the proper resistor to protect it .

11-30-2019, 10:32 AM	#41
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,426	Re: 12 volt coil with resistor The math looks close enough for me per Ohms law. For Ranchero50 The resistor wires were used by all the big 3 and probably others too. The heat was dissipated over the length of the resistor wire so it wasn't all in one spot. I'm not sure what the coil specs were for those systems either. The mounted ballast is usually 1.3 to 1.5 Ohms and are easy to work with for a 1.5 Ohm coil. I prefer to use the components I know for building a system from scratch. On a GM engine, I'd use an HEI type system with 12-volt. On a Ford engine, I'd use what ever came with that engine unless it has an old Load-O-Matic. Those systems were tied to the carburetor and don't work well without the original carb. The type of vacuum advance signal also has to be considered. Many conventional breaker types can be changed to electronic systems if a person doesn't want points & condenser. A person always has to keep in mind that a 6-volt system runs at around 7.1 to 7.6-volts in operation. The 12-volt systems are closer to 14-volts in operation with the generator or alternator on line. Last edited by rotorwrench; 11-30-2019 at 10:40 AM.

11-30-2019, 04:18 PM	#42
Purdy Swoft Senior Member Join Date: May 2010 Location: Alabama Posts: 8,099	Re: 12 volt coil with resistor If the ignition switch is left on without the engine running , if the points are closed the coil will get hot whether a resistor is used or not . When a resistor is used with a six volt 1.5 ohm coil , the resistor prevents full voltage from entering the coil . If full 12 volt voltage was connected to a six volt coil it would burn out the coil unless it had the proper resistor to protect it . Last edited by Purdy Swoft; 11-30-2019 at 10:18 PM.