*davies144*
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| posted on 9/6/09 at 09:04 PM |
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making sure the coil isnt buggerd
hi can you measure to see if the coil is goosed by measuring the resistance? any help will be greatly appreciated cheers ben
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MakeEverything
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| posted on 9/6/09 at 09:21 PM |
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Yes. A HAynes manual will tell you what the resistance should be around the primary coil.
If in doubt, replace it. Youll be chasing your tail otherwise.
I suspected the coil, but changed it last after changing the plugs, leads, points, condenser, then coil.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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02GF74
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| posted on 9/6/09 at 09:22 PM |
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firstly you are talking old fashion coil and not coil pack?
with coil, disconnect all wiringto it amd measure resistance across low tension side, between + and - terminals.
this should be 3 ohm for non ballast coil and 1.5 for ballast coil.
remove lead from + terminal and put lead into the central HT terminal, resistance should be several K ir not tens of K Ohm.
obviously readings of 0 ohm = short circuit or off the scale = open circuit, mean coils is buggered.
Bear in mind coils can seem ok when cold but when hot, due to expansion of stuff inside can fail but if they fail the cold test, then definetley
buggered.
Do not attempt to take coil apart as they are full of nasty oil.
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*davies144*
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| posted on 9/6/09 at 09:25 PM |
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hi yeh its an old fashioned coil for a pinto with electronic dizzy, sorry for being thick but whats the difference between a ballast/non-ballast coil
cheers ben
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02GF74
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| posted on 9/6/09 at 09:46 PM |
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ballast coil has lower resistance and is designed to work on 9 V.
this is to improve starting, since when cranking the engine over, the battery voltage can drop several volts below 12 V.
in order to prevent the coil getting too hot and buring out when runing, a resistor - looks like a thick piece of wire in the loom - is switched
in.
obviously when cranking, the ballast resistor is switched out. this was introduced to a lot of cars in the 1970s.
non ballast pre-dates that and has coil connected directly to 12 v.
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MikeRJ
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| posted on 9/6/09 at 11:23 PM |
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quote:
Originally posted by 02GF74
this should be 3 ohm for non ballast coil and 1.5 for ballast coil.
This is correct for points ignition. For modern constant energy electronic systems the coil will have low primary resistance (1.5 ohm or lower in
many cases), but is not used with a ballast resistor. The ignition amplifier limits peak current by adjusting dwell period.
Note that even if primary and secondary resistance is ok, this doesn't tell you if the coil is breaking down internally under high voltage or
has shorted turns which are the most common failures.
Your right about the oil in them, horrible stuff and I wouldn't be surprised if the older coils had PCB based oils in them (really nasty stuff).
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