Posted By: copper74
what is the purpose of a ballast resistor? - 08/19/09 07:40 PM
what is the purpose of the ballast resistor? can they be jumped?
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what is the purpose of the ballast resistor? can they be jumped?
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what is the purpose of the ballast resistor? can they be jumped?
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To constantly fail thus requiring you to keep a spare in your glove box.......at least thats what I have always been told
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To constantly fail thus requiring you to keep a spare in your glove box.......at least thats what I have always been told
lol. isn't that the truth
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Never had a ballast resistor problem in my 30yr Mopar life.
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And now, for the CORRECT answer. Ballasts change resistance with current as they heat and cool, and thus provide a sort of buffer for the coil. Coil current will be different at higher and lower RPM.
But the REAL nitty gritty reason is "easier starting."
A normal system runs close to 14V, and Mopar coils used to run anywhere from 8-10V AT THE COIL at the bottom end of the ballast.
When you crank the engine for start, the switch bypasses the resistor, so the coil STILL GETS about 10V--so a nice hot spark for starting.
This is something the ol' 6V cars never had.
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The ballast resistor also drops some of the voltage but voltage reduction is not its primary function.
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Automotive coils are current-driven devices. In the days of points, if the ignition system were left powered up with the points in the closed position (the key left on with the engine not running), the coil would effectively short out the battery and the coil would overheat. The ballast is a series resistor which limits the current in the coil. The ballast resistor also drops some of the voltage but voltage reduction is not its primary function.
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what is the purpose of the ballast resistor? can they be jumped?
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Well just out of curiosity, what did GM and Ford use so as not to burn out coils ????
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i dont agree with the post that says a ballast resistor is supposed to change resistance with temperature. .
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i dont agree with the post that says a ballast resistor is supposed to change resistance with temperature. .
You might not agree but you would be wrong. The fact that a BALLAST changes resistance is the entire reason it's called a ballast. Otherwise it would simply be a resistor. MOST resistors used in electronics are intended NOT to change resistance, even though they do somewhat, but they are NOT "BALLAST" resistors.
In the case of Chrysler, this is exactly what they are. Somewhere in the pile of old books around here, I've got documentation to back this up. I am NOT gonna spend time looking for it
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i dont agree with the post that says a ballast resistor is supposed to change resistance with temperature. .
You might not agree but you would be wrong. The fact that a BALLAST changes resistance is the entire reason it's called a ballast. Otherwise it would simply be a resistor. MOST resistors used in electronics are intended NOT to change resistance, even though they do somewhat, but they are NOT "BALLAST" resistors.
In the case of Chrysler, this is exactly what they are. Somewhere in the pile of old books around here, I've got documentation to back this up. I am NOT gonna spend time looking for it
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Home > Library > Science > Sci-Tech Encyclopedia
A resistor that has the property of increasing in resistance as current flowing through it increases, and decreasing in resistance as current decreases. Therefore the ballast resistor tends to maintain a constant current flowing through it, despite variations in applied voltage or changes in the rest of the circuit. See also Resistor.
The ballast action is obtained by using resistive material that increases in resistance as temperature increases. Any increase in current then causes an increase in temperature, which results in an increase in resistance and reduces the current. Ballast resistors may be wire-wound resistors. Other types, also called ballast tubes, are usually mounted in an evacuated envelope to reduce heat radiation.
Ballast resistors have been used to compensate for variations in line voltage, as in some automotive ignition systems, or to compensate for negative volt-ampere characteristics of other devices, such as fluorescent lamps and other vapor lamps. See also Fluorescent lamp; Vapor lamp; Voltage regulator.
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i dont agree with the post that says a ballast resistor is supposed to change resistance with temperature. .
You might not agree but you would be wrong. The fact that a BALLAST changes resistance is the entire reason it's called a ballast. Otherwise it would simply be a resistor. MOST resistors used in electronics are intended NOT to change resistance, even though they do somewhat, but they are NOT "BALLAST" resistors.
In the case of Chrysler, this is exactly what they are. Somewhere in the pile of old books around here, I've got documentation to back this up. I am NOT gonna spend time looking for it
According to Wikipedia, a ballast resistor can be fixed or variable . The Mopar variety are probably variable to adjust for the different secondary current needed to fire the plugs under different loads.
http://en.wikipedia.org/wiki/Electrical_ballast
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Can anybody remember when points used to make a pit on one point and a pile on the other?Ah the good old days when you had to file your points and use a dwell guage to set them.How about the compasiter(how you like that spelling?)that would soak up some of the voltage to keep the points from pitting and you could even adjust your mechanical voltage regulator according to which point had the pile on it and which had the pit.And after all these years I always thought that the ballast cut the voltage to the coil AND THE POINTS to reduce arching at the points.Man,thats old school!!
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what is the purpose of the ballast resistor? can they be jumped?
Save the coil from max voltage on normal drive, graduating the voltage level as far the enviroment is getting hot at engine bay. With hotter enviroment, gas needs less spark power to ignition.
On Start up moment, resistor is bypassed from ign switch, feeding directly the coil at brown wire spliced at resistor, to max voltage, being engine/gas is theorically cold and harder to burn out.
ballast has NOTHING TO DO with distributors &/or modules, JUST with coils.
Double ballast have the secondary voltage to ECU, I guess to JUST graduate the dwell or something like that on spark control system, but I don't think to really FEED it. There is ppl who has been able to run 5 pins modules with single ballast, what does not mean was working good or perfect. 4 pins modules have the secondary resistor built in.
On multi spark systems, the multi sparks setup makes not to get full power constantly during teh spark moment, so every milisecond between sparks gets the time to get cold at least enough to not burn out the coil. At the ends works like a time dimmer, or a voltage relay regulator ( mechanical regulator ) but NOTE: not with the same object, That it was to give you an idea.
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From the same Wiki article.
Self Variable Resistors
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On a points dist, all the power that goes to the coil passes through the points. Running constant 12v through the points usually burns the points up faster.
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On a points dist, all the power that goes to the coil passes through the points. Running constant 12v through the points usually burns the points up faster.
somehow true but also false... there is not anykind of points able to drive 15K volts from a coil, even less 45K volts. Neither 1K volts. Barelly can drive 12 Volts, and coil produces between 15K to 45K volts depending on performance.
Points makes a "small" volt level impulse AMPLIFIED by the coil and then routed back to distributor center cap center contact, rotor etc...
The voltage impulse is a SHORT ( by a ground contact ) made with the energy saved at condenser...
the - terminal at coil EFFECTIVELLY gets ground by the small short to create the amplified magnetic field variation going through and routed by the spark plug wires to the plug.
BUT EVEN IN THAT WAY still with electronic ( not points ), ballast is regulating the output at coil output to plugs at same ratio.
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Well just out of curiosity, what did GM and Ford use so as not to burn out coils ????
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On a points dist, all the power that goes to the coil passes through the points. Running constant 12v through the points usually burns the points up faster.
somehow true but also false... there is not anykind of points able to drive 15K volts from a coil, even less 45K volts. Neither 1K volts. Barelly can drive 12 Volts, and coil produces between 15K to 45K volts depending on performance.
Points makes a "small" volt level impulse AMPLIFIED by the coil and then routed back to distributor center cap center contact, rotor etc...
The voltage impulse is a SHORT ( by a ground contact ) made with the energy saved at condenser...
the - terminal at coil EFFECTIVELLY gets ground by the small short to create the amplified magnetic field variation going through and routed by the spark plug wires to the plug.
BUT EVEN IN THAT WAY still with electronic ( not points ), ballast is regulating the output at coil output to plugs at same ratio.
the points are on the 12v PRIMARY side of the coil. not the high output SECONDARY side. so technically, he's right. all the primary power passes thru the points
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can a ballast resistor in a car drain the battery?