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Thread: How to test an ignition module

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    Forum Moderator Boudin's Avatar
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    How to test an ignition module

    Is there a way to test an ignition module with a simple multimeter? I know that they can be tested with equipment from the autoparts store, but I'm looking for information on how to test it yourself. The one I have is the standard 4 pin type found on Chevy/GMC sbc distributors. I currently have it out of the vehicle.

    Thanks.

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    Senior Member silverhairdeere's Avatar
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    1989 GMC 1500 (PROJECT CHEAP TRUCK)

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    Forum Moderator Boudin's Avatar
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    Thanks, cc. I am trying to male sure that my ignition module that I pulled was bad. Is there any way to check it now that it has been removed?

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    Forum Moderator Boudin's Avatar
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    I went to the auto parts store to have it tested and just my luck....they couldn't find the adapter needed to test it. I put a multimeter to it and noticed different ohm values on the 4 pins. Is there a way to tell if it is bad like this?

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    Senior Moderator chevychase's Avatar
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    You know we all have said should be from 800 to 1500 ohm,s of resistance. Since your post i have checked some 7 pin modules with no luck.
    Do not have a older 4 pin. I check from all pins .. all i could get was some random #,s. Researched what i came up with was only way to check if still in vehicle.
    When i get time.. going by a buddy who owns a garage see what he has to say.

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    Senior Moderator chevychase's Avatar
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    Well talked to my buddy .. he said hummm... Said he has seen on forums also where said to check for resistance . Wondered his self ?
    He going to look at some books.

  7. #7
    Forum Moderator Boudin's Avatar
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    Thanks, chevychase. I noticed ohm values ranging from 15000 to as little as 2000. Not sure what values I'm supposed to get or if one can tell if it is bad or not without current/voltage to it. Thanks for looking into this for me. I have looked on the net as much as I can without any results. All I find is testing in the vehicle.

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    Senior Moderator chevychase's Avatar
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    No can do... can not check resistance on ign. module. Have to check voltages in vehicle or have a pretty expensive piece of equipment.

  9. #9
    Senior Moderator chevychase's Avatar
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    Tried checking one for resistance... noticed i got different reading each time i check . Well they have resisters ect . in the module reacts to heat.
    Soooo if you are holding it the heat from your hand will get different reading... say it is laying on bench different... take out lay on hot hood different resistance.
    So the only way to check is in vehicle . Going to check in vehicle see what i come up with. Seems i have to much time on my hands..

  10. #10
    Senior Member onthethreshold's Avatar
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    things to test on an HEI...

    got a digital volt meter... remove the module.. set the volt meter to 2K ohms. probe the pick up coil connector..
    500 to 1500 ohms... before disconnecting the test leads.. flip the meter over to 20 volt AC scale.. spin the shaft... you should see over 1 volt ac.. if you don't post the results..

    the module has to have dielectric tune up grease under it...

    both screws have to be installed... and snug.. not overly tight. but snug.. the module is grounded through the module screws..

    when you changed the cap... did you move the ground strap that fits under the coil over to the new cap????

    can you check that the ground strap is properly installed... and that the hold down screw on the condenser is tight...

    did you change the rotor... they do burn through ... letting all the spark right through to the distributer shaft...


    got the distributer out????? got a set of jumper cables.?????? put the cap on without the spark plug wires..

    put a jumper cable on the distributer housing... the other end on the negative battery terminal... that is still hooked up to the body...

    take the other jumper cable.. hook it to the positive battery post.. the other end with a chunk of wire with a 1/4 inch push on terminal shoved onto the batt terminal on the cap...

    now that the housing is grounded.. and the cap has power to it.. turn it upside down.. rest it on the radiator core support.. spin the shaft... it will throw 3/4" arcs... if the distributer is working..

    Read more: it wont start - Chevy Forums at Chevy High Performance Magazine

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