Coils and ballast resistors
Discussion
Due to swopping an engine I have a mix of old a new parts including the coil that goes with the engine but I have no idea is it's 6v or 12v; if it's 6 I need to add a ballast resistor, so does anyone know if it's possible to tell if the coil is 6 or 12 v as there is no label on it!
(Please don't ask what the cars are ;-) one is 1951 and the other 1973, and it's too complicated to try and explain why what and how, but if you know the answer to the question it would help!)
Having typed this I think it might be easier to just buy a 12v coil and have done with it, but I'lll see if someone answers!
Cheers
(Please don't ask what the cars are ;-) one is 1951 and the other 1973, and it's too complicated to try and explain why what and how, but if you know the answer to the question it would help!)
Having typed this I think it might be easier to just buy a 12v coil and have done with it, but I'lll see if someone answers!
Cheers
This should help, 6 and 12 volt coils have a different resistance value between the (-) and (+) posts. 6 volt being about 1.2 Ohms and 12 volt being about 1.5 Ohms.
http://www.ytmag.com/articles/artint131.htm
Yesterday's Tractor Website said:
Ignition System
The coil is the only component of the ignition system affected when converting from 6 to 12 volts. Like the ammeter, the wires on the coil must be reversed. This means the negative (-) terminal of the coil is the one that connects to the distributor, while the positive (+) terminal connects to the ignition switch. Also, for the system to operate properly, the coil must also have the correct resistance value for use with 12 volts. Since there are several ways to accomplish this, there seems to be considerable confusion surrounding coil selection. Most of the confusion comes in when referring to “6 volt” coils versus “12 volt “ coils and the accompanying ballast resistor that is sometimes used. The important point to remember is:
The total resistance of the coil plus any external resistor (if used) should be 2.7 to 3.3 ohms for a 12 volt system. This level of resistance will maintain the correct voltage and amperage in the ignition circuit. Coil resistance is measured between the plus (+) and minus (-) terminals.
Most original equipment 6 volt coils are about 1.2 ohms, while most original equipment 12 volt coils are about 1.5 ohms. In order to get to the 2.7 to 3.3 ohm requirement, a ballast resistor such as a Napa ICR13 (Approx. 1.8 ohm) can be added to these type coils. Another approach is to eliminate the ballast resistor altogether by using a replacement coil with 3.0 ohms of resistance.
Taken from here:The coil is the only component of the ignition system affected when converting from 6 to 12 volts. Like the ammeter, the wires on the coil must be reversed. This means the negative (-) terminal of the coil is the one that connects to the distributor, while the positive (+) terminal connects to the ignition switch. Also, for the system to operate properly, the coil must also have the correct resistance value for use with 12 volts. Since there are several ways to accomplish this, there seems to be considerable confusion surrounding coil selection. Most of the confusion comes in when referring to “6 volt” coils versus “12 volt “ coils and the accompanying ballast resistor that is sometimes used. The important point to remember is:
The total resistance of the coil plus any external resistor (if used) should be 2.7 to 3.3 ohms for a 12 volt system. This level of resistance will maintain the correct voltage and amperage in the ignition circuit. Coil resistance is measured between the plus (+) and minus (-) terminals.
Most original equipment 6 volt coils are about 1.2 ohms, while most original equipment 12 volt coils are about 1.5 ohms. In order to get to the 2.7 to 3.3 ohm requirement, a ballast resistor such as a Napa ICR13 (Approx. 1.8 ohm) can be added to these type coils. Another approach is to eliminate the ballast resistor altogether by using a replacement coil with 3.0 ohms of resistance.
http://www.ytmag.com/articles/artint131.htm
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