The Ford Barn

backrodebob · 06-08-2021, 09:30 PM

QUESTION? 12 v system, external 1.5 resistor with 1.5 coil or 3.0 coil pros cons or personal preference? some say 3.0 gets hotter? true or not?

51504bat · 06-09-2021, 08:00 AM

On my '39 p/u with an 8ba converted to 12 volts I'm using a 012 Bosch Blue internal resister coil. Works great with no issues. Just my experience.

JSeery · 06-09-2021, 12:02 PM

The 3.0 ohms coils are easier to install, but there are advantages to a resistor + coil setup. That is why Ford used a resistor with the original 6v coils. The resistor varies the resistance as it heats up, so there is more voltage going to the coil at startup. If you really want to go whole hog, add a later model starter solenoid. This is the arrange Ford used on the later 12v vehicles. The solenoid setup bypasses the resistor for full battery voltage to the coil while the starter switch in engaged. As soon as the switch is released the coil voltage is dropped down by the resistor.

rotorwrench · 06-10-2021, 07:31 AM

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If all is working well, the coil will not increase in temperature all that much and even if it does, the modern coils generally use an epoxy internal insulator instead of tar like the old coils did. When the coil is in operation, the magnetic field is getting broken multiple times per second. They only get hot when the points are closed and the ignition switch is on when the engine isn't running as a general rule. Now if something is wrong inside the coil like a cracked primary winding wire, then the resistance of the primary increases and that can lead to overheating. Eventually the coil will cease to function if the primary is damaged.

06-08-2021, 09:30 PM	#1
backrodebob Member Join Date: Jul 2019 Location: Union City, CA Posts: 57	coil QUESTION? 12 v system, external 1.5 resistor with 1.5 coil or 3.0 coil pros cons or personal preference? some say 3.0 gets hotter? true or not?

06-09-2021, 08:00 AM	#2
51504bat Senior Member Join Date: Sep 2013 Location: SoCal-Redlands Posts: 3,018	Re: coil On my '39 p/u with an 8ba converted to 12 volts I'm using a 012 Bosch Blue internal resister coil. Works great with no issues. Just my experience. __________________ Making the simple complicated for over 30 years.

06-09-2021, 12:02 PM	#3
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: coil The 3.0 ohms coils are easier to install, but there are advantages to a resistor + coil setup. That is why Ford used a resistor with the original 6v coils. The resistor varies the resistance as it heats up, so there is more voltage going to the coil at startup. If you really want to go whole hog, add a later model starter solenoid. This is the arrange Ford used on the later 12v vehicles. The solenoid setup bypasses the resistor for full battery voltage to the coil while the starter switch in engaged. As soon as the switch is released the coil voltage is dropped down by the resistor.

06-10-2021, 07:31 AM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,431	Re: coil Sponsored Links (Register now to hide all advertisements) If all is working well, the coil will not increase in temperature all that much and even if it does, the modern coils generally use an epoxy internal insulator instead of tar like the old coils did. When the coil is in operation, the magnetic field is getting broken multiple times per second. They only get hot when the points are closed and the ignition switch is on when the engine isn't running as a general rule. Now if something is wrong inside the coil like a cracked primary winding wire, then the resistance of the primary increases and that can lead to overheating. Eventually the coil will cease to function if the primary is damaged.