QuestionQUESTION: I have taken the ballast resistor out of the ignition circuit on my '76 Spitfire 1500 and gone with an Accel 12V coil and the same Lucas 45D4 distributor. Since then I've gone through 2 sets of points. Are these related? Would 12V to the previously 6V points/condenser cause a problem? Thanks
ANSWER: Hi Brian,
The points don't care what voltage coil is used but the condenser may because the job of the condenser is to bleed off the reverse surge of current in the coil after the field transfers to the secondary and to the spark plug. Since the windings in each coil are different, the serge of current is different.
If that is the cause I believe all you need to do is to get a condenser from an early MGB or A-H (they each had a different length wire because of how they were mounted in the distributor)to correct the problem.
There are two other things that can cause it and one is a leaking diode in the alternator (check your charge rate) and the other is a bad ground between the engine and body or body to battery.
Howard
---------- FOLLOW-UP ----------
QUESTION: Thanks for the info. What is the function of the drive resistor? I removed the one that was in my car with no wires going to it when I bought it. Thanks
AnswerIt is used because when a starter motor is engaged there is no longer 12v available to the coil, so they install a 6v coil and that solved the low voltage to the coil when starting. However that created another problem. When the key was released back to run, the starter was no longer running and now 12v was available to the coil and since it was now a 6v coil it would make the 6v coil get very hot and melt it down. So they added a resister to the coil and run a bypass wire from the starter solenoid bypassing the resister.
So now they would run the power direct to the coil in the start position and when the key was released the power would come from the key to a resister and on to the coil thus not overheating the coil.
Howard
