Coil question/problem

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Posts: 32
Joined: Sat Aug 21, 2004 9:52 pm
Location: Massachusetts

Coil question/problem


Post by bonham3 » Sat Jun 18, 2005 5:28 pm

I was wondering if i could get some help with my coil.
I run a 12V 3.0 ohm Dyna Coil and think it may be bad. Not sure.
I get a strong spark at one tower but a weak spark at the other
tower. I have new plugs and the wires are O.K.
I checked all this by pulling plugs and hooking up the plug wires
to them, grounding the plugs and turning my ignition on and off.
I run a mallory elec. dist.
I was having backfiring problems as listed in another post and wanted
to rule out or in any coil problem.
Thank's Bonham3 Ron L.

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Post by mbskeam » Sat Jun 18, 2005 8:07 pm

so you say that when you turn the ign on and off it fires the plugs?
I dont think this is correct , I have no exp with the mallory unit, but that dont seam right. the electronic part in the dist is a stanard maallory unit any auto parts store that deals with them can get you a new module, if that is the problem.
is it wired correctly? what is the coil ohm for this dist need to be? did you get it new with a set up sheet(specs) if all else fails read the instructions. LOL

some body on this site might know.

and for the coil it sounds like mine before I replaced it, it had heat related issues.but thats why I got it for free. put a new one on, and no problem any more.
spark should be even. got a buddy to lend you one?
you dont have to put it on the bike to test this, just get some small jumper cables to hook it up and you will know in less than 5 min if you have coil issues


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Location: Massachusetts

Coil problem question 2


Post by bonham3 » Sat Jun 18, 2005 9:12 pm


Distributor and module fine. Just put in a new module.
You would get no spark if module was bad or wired incorrectly.
I have a spare Dyna Coil but i think that one is bad also.
They both worked fine for a year and now this problem.
Still wanted my stupid question answered as to the proper wiring
at the coil terminal. There are no marks or pos./neg. etc. on the coil terminals. I get spark either way i hook up but do not want to
do any furthur damage :(
Just want to rule out the coil before i have to shell out for new one.
About that off bike test? How to proceed? Jumpers frpom where to what???
Thank's Bonham3 Ron L. Mass.

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2012 Heritage Softail Classic
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Post by Red55FL » Sun Jun 19, 2005 1:13 am

I have the spec sheet for the Mallory ignition that came with my bike & it calls for a 2 to 4 ohm coil. The coil that was on my bike when I got it was a 4.7 ohm & the spark was very weak. A 3 ohm should work fine.
Since there are no + or - markings on the coil, it won't matter which terminal is hooked to power as neither terminal is internally grounded as some coils are. That is why it works either way.
The reason that the coil fires when you turn off the switch is that with the switch on, power is flowing through the coil primary windings. When the switch is turned off it has the same effect as opening a set of points, the electrical field breaks down causing a power surge in the coil secondary windings and a spark.
Since you have a good spark from one coil tower and a weak spark from the other, it is safe to say that the coil is bad. As mbskeam says, the spark should be even.


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