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Ballast Resistor System


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#1 haggz

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Posted 15 December 2010 - 10:33 AM

just reading a topic on modern ignition systems and thought that this would be of help and make things clearer for us non tech mini owners.

this is just a breif part covering the '' ballast resistor system ''

The first improvement to the basic coil, points, and condensor set-up occured in the late sixties/early sevenies, when an extra component was added: THE BALLAST RESISTOR. In practice , this was rarely an actual resistor, but usally a special piece of cable (between the ignition switch and the coil) with higher than normal electrical resistance. And the whole idea was to make the coil run at roughly half the cars normal voltage. The big question , your proberly wondering is '' why''.
Well forget the usual rubbish thats often trotted out - such as '' it keeps the coil cool'' , or '' stops so much electricity being used''-
because Ballist resistor system use different coils with different windings to still create the 20,000 or so volts needed at the plugs. Their big advantage , though, is that they produce a much stronger spark during cranking. In contrast , conventional systems produce a weaker spark during starting.
This is because conventional coils are designed to work at around 14 volts- normal engine and alternator running voltage. but during cranking, battery voltage can drop as low as 9 volts, which means the coil is seriously down on input voltage. So much so, there may be insufficient voltage for a decent spark if the battery becomes run down.

On a ballast resistor system, whose coil is designed to usally run at 6-7 volts from the resistor cable, a separate feed from the same circuit as the starter solenoid temporarily feeds the coil during cranking. Obviously this temporary feed will be at battery voltage of 9-11 volts during cranking. So in effect, the coil runs at 'boost' voltage during cranking rather thanat reduced power in a conventional system.

One easy way to spot if a ballist resistor system had been installed is to look at the coil. If there are two connections on the POSITIVE side, one will proberly be from the 'resistor' feed, and the other will come from the starter circuit.

After reading this myself, i now no what the difference is between the coils that people enquire about and maybe might help someone who is having starting problems, weak spark etc.

#2 camp freddy

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Posted 15 December 2010 - 06:48 PM

just reading a topic on modern ignition systems and thought that this would be of help and make things clearer for us non tech mini owners.

this is just a breif part covering the '' ballast resistor system ''

The first improvement to the basic coil, points, and condensor set-up occured in the late sixties/early sevenies, when an extra component was added: THE BALLAST RESISTOR. In practice , this was rarely an actual resistor, but usally a special piece of cable (between the ignition switch and the coil) with higher than normal electrical resistance. And the whole idea was to make the coil run at roughly half the cars normal voltage. The big question , your proberly wondering is '' why''.
Well forget the usual rubbish thats often trotted out - such as '' it keeps the coil cool'' , or '' stops so much electricity being used''-
because Ballist resistor system use different coils with different windings to still create the 20,000 or so volts needed at the plugs. Their big advantage , though, is that they produce a much stronger spark during cranking. In contrast , conventional systems produce a weaker spark during starting.
This is because conventional coils are designed to work at around 14 volts- normal engine and alternator running voltage. but during cranking, battery voltage can drop as low as 9 volts, which means the coil is seriously down on input voltage. So much so, there may be insufficient voltage for a decent spark if the battery becomes run down.

On a ballast resistor system, whose coil is designed to usally run at 6-7 volts from the resistor cable, a separate feed from the same circuit as the starter solenoid temporarily feeds the coil during cranking. Obviously this temporary feed will be at battery voltage of 9-11 volts during cranking. So in effect, the coil runs at 'boost' voltage during cranking rather thanat reduced power in a conventional system.

One easy way to spot if a ballist resistor system had been installed is to look at the coil. If there are two connections on the POSITIVE side, one will proberly be from the 'resistor' feed, and the other will come from the starter circuit.

After reading this myself, i now no what the difference is between the coils that people enquire about and maybe might help someone who is having starting problems, weak spark etc.



good bit of info , needs pinning

#3 MiniVespa

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Posted 02 January 2011 - 04:27 AM

great info here on the system. because you seem to know plenty about it, i have a question for you.

i have a 89 british racing mini. it has the ballast resistor system and 4 pronged coil. the 998 engine that was in it was pulled out and i put a 1275 in that is a bit older. the coil and loom was retained. after hooking it all up, now my tach isnt working and i have a feeling it has to do with how its hooked up to the coil. any help here? cheers!

#4 afhuey

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Posted 22 April 2011 - 01:48 AM

On my car, I could not visually differentiate what type of coil I had. I was also confused if my car was wired for a ballast. So, after some research, I came across some mini specific info and I would like to pass it on to further help people with their woes.

I will go through the steps you should take for troubleshooting your coil system. First, find out what type of coil is currently on the car. Second, find out what type of coil your car is wired for. Third, determine if your car is setup correctly.

Telling a ballast coil vs. non-ballast coil:
A1) Disconnect all of the wires from your coil (label them if you are unsure of where they go). All you want to see is the coil, the two posts and a HT recepticle.
A2) Use a multimeter and switch it to Ohms (looks like an upside down horseshoe).
A3) Place one lead on the + terminal and one lead on the - terminal.
A4) If you have 3 ohms, you have a 12v non-ballasted "standard" coil.
A5) If you get between 1-2 ohms, you have a 9v ballasted coil.
A6) If you get several thousand ohms, you are hooked up wrong and have it connected to the HT recepticle. Redo step A3.
A7) Now reattach all of the wires.

Telling if your car is supposed to be ballasted or non-ballasted:
NOTE: Ensure your battery is fully charged with at least 12v prior to testing.
B1) Visually look at the wires attached to the coil. If your + post on the coil has two wires and one is either pink or pink and white, you probably have a ballasted system. If you have a wire running from your starter solenoid to the coil, you probably have a ballast type system. If you have a white ceramic brick attached to the coil, you probably have a ballast type system. Proceed to step B2 to make sure everything is working correctly.
B2) Securely connect a jumper wire from your earthing strap to the - post of your coil.
B3) Connect your multimeter leads to the + post of the coil and the earthing strap (not directly to the jumper wire but near it).
B4) Turn your multimeter to Volts DC (VDC) some times an = with a dashed line above it (not = with a wavy line above).
B5) Turn your key in the ignition to "ON" (NOT START) and look at the multimeter.
B6) If you have 12v, then you have a non-ballasted "standard" system.
B7) If you have a voltage of 6v-9v (or a little higher but not above 10v) then you have a ballasted system.
B8) Turn your key "OFF" (never leave your key in the "ON" position for too long, your coil might overheat)

So what coil are you supposed to have on your car?:
C1) If you have 12v like in step B6 then you are supposed to have a 3ohm coil like in step A4. If this is correct, then you are good.
C2) If you have 6v-9v like in step B7 then you are supposed to have a 1-2ohm coil like in step A5. If this is correct, then you are good.
C3) If you have 12v like in step B6 and a 1-2ohm coil like in step A5, then you need a non-ballasted "standard" coil because your system is running with too much voltage and you will burn out your coil and/or points if you continue running like this.
C4) If you have 6v-9v like in step B7 and a 3ohm coil like in step A4, then you need a ballasted coil as your system is running with too little voltage and producing a weak spark.
C5) If you have an inline external ballast (white ceramic brick) then you need to verify that the input power to the brick is 12v, the output is 6-9v and your coil is 1-2 ohm (like in step A5). You also need to verify that the ballast is wired into the ignition wire and not the wire from the starter solenoid. And finally you need to verify that you have two wires, one wire from your ignition and one wire from your starter solenoid, connected to the + post of the coil (two wires). If all this matches, then you are good.

I tried to make this as non-confusing as possible. This is my first how-to post and I wanted to help people with something that I learned and struggled with on my car. Hope this helps someone.

Edited by afhuey, 22 April 2011 - 04:49 AM.





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