[DeTomaso] coil resistor

[SOBill at aol.com]

Here's the scoop on why coil (ballast) resistors  exist:
 
Points style ignitions and some electronic ignitions are designed  to 
operate with 8 volts on the coil positive terminal. The ignition is designed  to 
operate on 8 volts because that is all the voltage we are likely to have 
when  the battery is out in freezing temperatures and we are trying to start 
the  engine. The 8 volts is obtained, when the engine is  running, by placing 
a resistor between 12 volts from the RUN position  of the ignition switch 
and the ignition coil.
 
When the engine is being started, the battery voltage will drop as  low as 
8 or 9 volts and the ignition coil, thru the resistor,  would get only 
around 5 volts ......... 5 volts is not enough. So, on the  starter solenoid the 
small right hand terminal gets battery voltage  while the starter is 
cranking. This battery voltage ( 8 or 9 volts) from the  small right hand terminal 
on the starter solenoid is wired to the coil  positive terminal, bypassing 
the resistor while the engine is being started. Now  the ignition has the 
required voltage.
 
Cars have been built this way for decades.
 
MSD ignitions do not require any ballast resistor. MSD ignitions  are 
capacitive discharge ignitions which dump several hundred volts into  the 
ignition coil to fire the plugs and can do this even when the battery  voltage is 
low during engine cranking.
 
Have fun.
 
SOBill  Taylor
sobill at aol.com  



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