Hi, I'm looking to replace my ignition coil. I have a 1990 mini studio 2 and have noticed when looking for a new coil some are ballast and others aren't. I have no idea what this means and if I need one which is ballast!
Many thanks
Tim
Ignition Coil - Ballast Or Not?
Started by
Timmytimtim
, Nov 16 2011 08:09 PM
3 replies to this topic
#2
haggz
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Speeding Along Now
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Posted 16 November 2011 - 08:14 PM
i posted this last november, it may make sense, but im sure someone will be along soon with more knowledge and electrical understanding
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.
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.
#3
Timmytimtim
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Learner Driver
Posted 16 November 2011 - 08:29 PM
Hi, thank you very much for that response. Did a search but couldn't find it but my fault for not doing 'over 30 days' search. I'll know for next time 
)
)
#4
dklawson
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Posted 17 November 2011 - 02:00 AM
As I told you in your other thread, do not assume the coil is bad. Always save coil replacement for last after you have replaced all the other (and less expensive) ignition parts. Also, only replace ONE item at a time. Never change everything at once when trying to troubleshoot a problem.
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