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Thread: Ignition Coil Resistance

  1. #1
    DX User Sandwich's Avatar
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    Question Ignition Coil Resistance

    Hey guys,

    bit puzzled, checked old and new ignition coil resistances, both within regions for secondary winding resistance (A & top) , B & D resistance & continuity.

    But both out for primary winding resistance (A & D), both at 1.8 Ohms, instead of between 1.215-1.485 k Ohms according to manual specs.

    checked the part i bought on RockAuto: https://www.rockauto.com/en/moreinfo...500&cc=1166969
    that claims it should be between just 1.2-1.8.

    Is the manual wrong or have I misinterpreted it? Cheers

    -coil_manual-jpg



  2. #2
    DX User Sandwich's Avatar
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    Re: Ignition Coil Resistance

    If anyone fancies giving their coil a quick test with a multimeter for comparison that would be super helpful!

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    Re: Ignition Coil Resistance

    No the new ones wrong.

    I went thru it with Standard auto parts a few years ago and the basically told me to buzz off.

    They told me if I could come up with the original 30? year part they would look into it. Sadly I just found the original a few months ago but I havent followed up with those idiots. But mine measures very close to the book spec where all the news ones I have gotten dont.
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    DX User Sandwich's Avatar
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    Re: Ignition Coil Resistance

    Quote Originally Posted by Oldblueaccord View Post
    No the new ones wrong.

    I went thru it with Standard auto parts a few years ago and the basically told me to buzz off.

    They told me if I could come up with the original 30? year part they would look into it. Sadly I just found the original a few months ago but I havent followed up with those idiots. But mine measures very close to the book spec where all the news ones I have gotten dont.
    close to book spec as in, in the thousands like suggested or more 1.2-1.4 ohms?
    Last edited by Sandwich; 11-01-2020 at 09:35 AM.

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    Re: Ignition Coil Resistance

    A-D im getting .4 ohms on the new UF63 Standard auto parts coil.

    On the primary side im getting nothing...its open.

    Refreshing my memory I think thats why I called them to start with it was bad out of the box. When I bought another parts store one it was also out of spec from all the books I have so I stuck with what I have on the car.
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    Re: Ignition Coil Resistance

    Just a note,and im not an Electrical engineer but the reason this could be bad is it loads the rest of the circuit and could make your ICM fail.
    1988 Lxi owner since August 1995
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  7. #7

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    Re: Ignition Coil Resistance

    Quote Originally Posted by Oldblueaccord View Post
    Just a note,and im not an Electrical engineer but the reason this could be bad is it loads the rest of the circuit and could make your ICM fail.
    There needs to be some isolation between A and D. D is essentially a ground that the ICM completes when the reluctor makes a pass, .4ohm could likely overcurrent the ICM and cause a poor charge on the secondary. A and the ignition coil post should clearly show high resistance as its a massive coil of wire, 100x some more turns than the primary. Standard auto parts is just ignorant, you could hand them any ignition coil and see a couple ohms on the primary and several thousand on the secondary, the book is right.
    Last edited by ShiRen; 11-02-2020 at 02:43 PM.

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    DX User Sandwich's Avatar
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    Re: Ignition Coil Resistance

    yeh mine seems all good for B&D and the others, its just the A&D that seems out, manual suggests in the thousands but im sitting at 1.8 ohms, on both. you able to check what your coils running with a multimeter for comparison ShiRen? would be quite interesting to see the variation. Cheers

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    Re: Ignition Coil Resistance

    I pitched my stock coil, I'm running MSD. I didn't notice the manual has a comma in the A&D test, that's a bit odd. I wouldnt think the stock coil would have enough primary windings to bring the resistance up to 1kohm, but then again I am not sure why it has a 2.2kohm resistor in it across B&D (I was referring to A&D in the beginning of my last post, A is bat+, B is tach, I will fix that). This is a pretty standard coil, I would not write it off for ~1ohm primary resistance.

    A normal coil will look like this, and you can use one if you like.

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    Re: Ignition Coil Resistance

    Quote Originally Posted by ShiRen View Post
    I pitched my stock coil, I'm running MSD. I didn't notice the manual has a comma in the A&D test, that's a bit odd. I wouldnt think the stock coil would have enough primary windings to bring the resistance up to 1kohm, but then again I am not sure why it has a 2.2kohm resistor in it across B&D (I was referring to A&D in the beginning of my last post, A is bat+, B is tach, I will fix that). This is a pretty standard coil, I would not write it off for ~1ohm primary resistance.

    A normal coil will look like this, and you can use one if you like.
    I gotta ask someone smarter than me what the 2.2k ohm resistor is about. I can see it in the epoxy on one of the stock ones I have. Wild guess its something to do with noise.
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    Re: Ignition Coil Resistance

    I am assuming it is a current limiting resistor. You know, I am wondering now if that is why I once got my cruise control to work for about 2 seconds, but I don't remember which coil I was using when I was working on that. Nothing bad has happened to my tach or fuel pump. So beware, if you put an aftermarket coil on you might kill the cruise control, maybe, who knows, do tell.

  12. #12
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    Re: Ignition Coil Resistance

    Ok, I think both my coils are in spec (enough) then, gonna keep a hold of them for now. My focus for the other thread https://www.3geez.com/forum/3geez-ac...ml#post1221750 is to check the vacuum diaphragm and timing this weekend, fingers triple crossed. Cheers for your knowledge on this guys

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    Re: Ignition Coil Resistance

    Quote Originally Posted by ShiRen View Post
    I am assuming it is a current limiting resistor. You know, I am wondering now if that is why I once got my cruise control to work for about 2 seconds, but I don't remember which coil I was using when I was working on that. Nothing bad has happened to my tach or fuel pump. So beware, if you put an aftermarket coil on you might kill the cruise control, maybe, who knows, do tell.
    This post is like Vizzini try to decide whether to drink from the glass in front of him, or in front of the Dread Pirate Roberts in The Princess Bride. Truly dizzying! ;-)
    Dr_Snooz

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    Re: Ignition Coil Resistance

    Being scatterbrained and tangential are quality traits of mine

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