1966 coil resistor 1966 427/390
I purchsed a coil (ballast) resistor for my 1966 427/390 from one of the major parts vendors. When we tested it installed on the car, the voltage drop was only 11 volts, not the 6 or so volts from the original. It looks like the same supplier furnishes these to the industry. Does anyone carry a correct resistor and has anyone else had this problem? Thanks.
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Re: 1966 coil resistor 1966 427/390
11 was the voltage drop across the coil or the ballast?
Use a good digital meter to measure ballast resistance. It should be about 1.8 ohms at room temp. If it is 0.3 ohms you have the wrong ballast for your coil.
Duke -
Re: 1966 coil resistor 1966 427/390
Also, remember the ballast resistor is a simple passive component and NOT an active element like a 3-legged voltage regulator that can/does dictate a specific output voltage. The ballast forms a voltaqe divider chain in conjunction with the ignition coil's primary windings and the specfic contact resistance of the ignition points.
Therefore, it takes ALL of the ignition components to be 'correct' in terms of their resistance profiles AND the voltage regulator/alternator to be behaving properly for you to measure a SPECIFIC voltage level at the coil....Comment
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Re: 1966 coil resistor 1966 427/390
Just to elaborate on Jack's point, the ballast resistor is in series with the resistance of the primary winding in the coil. If the ballast resistor is 1.8 ohms and the coil primary is 1.8 ohms, you can expect half of your nominal 12 volt supply to drop across the ballast resistor. If the result you are getting is not what is expected, it could be because either the ballast resistor or the coil is incorrect.
Also, note that you can only measure this voltage drop with the engine off, the ignition on, and the points closed. Since the points are opening and closing while the engine runs, the voltage across the ballast resistor will be rapidly changing while the engine is running. If you manage to stop the engine in a postion where the points are open, there will be no voltage drop at all across the ballast resistor.Comment
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