If your car uses a 12 volt battery, the 12 volts you put into the primary side of the coil will exit the secondary side as 30,000 volts! Many restorers modify the lock switch system by using a conventional coil and routing the hot wire through the armored cable. A coil with the correct turns ratio to work right with one type of ignition system may not be the best solution for a different type of system. The high voltage is carried away from the coil by a high-tension cable that looks like a short piece of spark plug cable and runs to the distributor tower. For factory-type repair of a lock switch extension coil you may be able to find a swap meet vendor with a coil service package for your car. Dwell isn't swell. MSD, A Holley Brand; El Paso, TX; 888.258.3835; Holley.com/brands/msd, By clicking Sign Up, you agree to the  Terms of Use. Before we begin this discussion, let’s talk a bit about electricity in general. It has an iron core with fairly thick wire (primary winding) wrapped around it a few hundred times. The coil becomes a transformer, stepping the voltage up. As the magnetic field continues collapsing, the electromagnetic phenomenon of inductance causes another current to flow in the secondary windings. Coils can be tested with an ohmmeter (most coils will give a reading around 8,000 ohms) or with the small scope on a Sun machine. However, more voltage does not always mean better in the world of ignition coils. The idea behind any ignition system is to generate an extremely high voltage -- on the order of 20,000 volts -- at exactly the right time. At some engine rpm point, the coil can't fully recharge before it becomes time to fire the next spark plug in the engine's firing order. Either way, somewhere in the 4-6 amp range while the car is running. In the example waveform, the voltage is about 14.0 volts. A lot of the older systems used 12 volts to the coil when the ignition switch was in the start position than when released to the on position the resistor alowed reduced voltage to the coil. Also note that as voltage output increases, current output decreases. Photo: MSD. See How Car Engines Work or How Two-Stroke Engines Work for details. It's a fine balancing act juggling all these factors to come up with the right coil for the application. The ignition coil has a resistor in series with it so you should measure around 9V when the points are closed. The iron core's laminations have many more thin metal layers to yield a higher-frequency coil with less energy loss. In the case … The magneto is the white block in the … ... You definitely do need it, or you will smoke your coil in short order by running it at high voltage (12+ volts) for long perods of time. At low rpm, 30 degrees of coil dwell time can be 2 or 3 times longer than needed, resulting in excess ignition system heat buildup and unnecessary alternator power consumption. Paging through an ignition catalog reveals all sorts of different ignition coils for conventional distributor-type ignition systems. Since a car ignition coil acts as a step-up transformer, the secondary coil has many more turns than the primary coil. This means that current moves in one direction, from the positive battery terminal to the negative battery terminal. 5. A "hot" coil runs...hotter: As coil output increases, so does its need to radiate heat. "). This posed a dilemma for the ignition … When an electric current flows from the battery to the primary coil, it gets repeatedly disrupted by the secondary coil creating a strong magnetic field that charges the secondary coil to a higher voltage than the initial 12 Volts that came from the car battery. The role of the ignition coil is to multiply battery voltage into high voltage. This winding lies inside the magnetic field created when electricity goes through the primary winding. The final voltage is about 12 volts - 2 volts lower than the original voltage. The voltage would not hurt it at any rate, the load or resistance of the coil windings will determine how much amperage the coil can withstand without burning out. Apparently 6 cyl car coils do not require the resistance and use the full 12 volts all the time. Your information will be collected and used in accordance with our  Privacy Policy. If your car has a Delco-Remy coil, Yesteryear ( ) in Port Charlotte, Fla., specializes in these kinds of parts and may be able to help. You should never need to open a sealed ignition coil. Perry. Some extremely high-output coils may only be used in short-duration drag racing, as compared with others optimized for long-duration oval track or an extended lifetime of street performance. The high voltage is carried away from the coil by a high-tension cable that looks like a short piece of spark plug cable and runs to the distributor tower. You should have no problem with it. What is a coil? But that's why they are so many choices out there! Engineers refer to a coil's time-charge factor as "dwell," which is expressed in crankshaft degrees. When the coil's primary circuit is switched on, the voltage drops slightly, and as the current in the circuit increases to the target of 11 amps, the voltage drops accordingly. Time waits for no mortal...or ignition coil. When you switch on the ignition and the breaker points are closed, current flows through the primary winding, creating a magnetic field. A common automotive ignition coil can generate an output voltage on the order of 30,000 volts. If oil starts leaking out, it's a sign that the coil's days are numbered. These kinds of coil problems are usually caused by heat and vibration. With a 100:1 turns ratio and, for example, an initial 250-volt current-interruption spike, in theory there would be a spark output of 25,000 volts (assuming no losses to resistance). Photo: Steve Amos. You cannot operate a car smoothly without delivering high voltage to the spark plugs to ignite the air-fuel mixture. Most coil failures result from secondary winding defects. This sends current through the secondary winding. The secondary output is a short very high amplitude pulse which fires the spark plug. Sometimes the thin lacquer insulation between the two windings deteriorates. With the ignition switch in the RUN mode. It takes an (ignition) village: In sum, to achieve maximum performance, the coil should be optimized for the type of ignition system employed (inductive or capacitive discharge) and distributor's switching mechanism (points or electronic), expected engine operating rpm range, and duty cycle (street, short-duration racing, or endurance racing). 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