Resistor Unit / Coil Resistor 6 Volt System

denns1989

denns1989

Member
Greetings Again

I searched & didn't find a clear answer for my current inquiry.

My car with a 1949 - 53 8BA 6 volt pos ground system didn't have a "resistor unit" as it's called in the manual or "coil resistor" as it is often referred to... I have rewired the car & just wanted to ask a couple questions.

I'm aware of the general rule that a 1.3 ohm coil is used on a 6 V system, however they were also used on 12 V system with a "ballast resistor" or you can use a 3 ohm coil direct on a 12 V system.

I think I understand that the coil resistor was designed to supply a full 6 volts when cold & then drop the voltage to roughly 4 volts so not to damage the ignition system? But why only on Fords when most other 6 V systems use a 1.3 ohm direct ?

My car had a "1.3ohm" coil without a "coil resistor" & I have to assume it worked, is the "coil resistor" only required when using an original coil that has a different internal resistance ?

I can just order a coil resistor & "original" coil but I wanted to understand if this is only necessary when using an "original coil" for the car or can you just use a standard 1.3 ohm coil & forget the coil resistor... if I upgrade to Petronix, they state to use on "non ballasted" systems with stock coil (not high voltage)... so once again I would assume this means with no "coil resistor"

Hope I'm making sense, thanks in advance
 
ahhh the Bosch Blue - same as I have on my MG Midget well regarded coil - Perfect !
So even though it's a "12 volt" coil it's fine to use direct on a 6 volt system ? Just wanted to be sure, makes sense though, total resistance will be the same as it would be with a resistor & 1.3 ohm coil.

Thanks
 
I believe the Bosch Blue was recommended if I had a 12 volt system ?, but for a 6 volt system the 3 ohm will be to much ? (only 2 amps on 6 volt)
Further research indicates that the coil resistor is only needed if using an "original" pre 48 coil that has an internal resistance that is less than 1 ohm (maybe 0.8?) But if using a regular "round can" coil no coil resistor is needed, just a 1.3 ~ 1.5 ohm coil typically referred to as a 6 volt coil (or 12 volt coil that needs an in line resistor.)
 
denns1989 said:
I believe the Bosch Blue was recommended if I had a 12 volt system ?, but for a 6 volt system the 3 ohm will be to much ? (only 2 amps on 6 volt)
Further research indicates that the coil resistor is only needed if using an "original" pre 48 coil that has an internal resistance that is less than 1 ohm (maybe 0.8?) But if using a regular "round can" coil no coil resistor is needed, just a 1.3 ~ 1.5 ohm coil typically referred to as a 6 volt coil (or 12 volt coil that needs an in line resistor.)
Click to expand...


Correct ...........:eek:
 
Most of the round 6 volt coils have a built in resistor so no external one is required. Many vehicles in the fifties had a "ballast" resistor so the ignition switch or solenoid could bypass it to give the engine better starting with higher voltage while the starter was running.
 
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