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Subject: Questions about Square Coils

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Farmer Dan    Posted 12-03-2018 at 17:32:02 [URL] [DELETE]        [Reply] [Email]  
  • Questions about Square Coils
  • Its been my experience that a coil either works or it don't no in between. I have at least 6 coils on my work bench and I have no idea if they are any good or not. I try to measure them with a digital multi meter and get a different reading from every one of them.

    What is a good way to measure them or test them. Guess I should have kept that tester I made LOL. Do these have any resale value or should I just give up and toss them in the trash Tuesday?

    RockyMO    Posted 12-06-2018 at 03:34:34 [URL] [DELETE]        [Reply] [Email]  
  • Re: Questions about Square Coils
  • There are several in betweens and all of them seem to be heat related. I have seen them good and fail when hot. I have also seen them good cold and cause a miss when hot. The easiest solution is indeed to put it on Maude and try it. Since you can't go outside and work on Maude, perhaps we should concentrate on bringing Maude inside to you. Now the 64 dollar question, do we disassemble and reassemble maude or widen your door way?

    Rocky in MO

    Tim Daley(MI)    Posted 12-04-2018 at 06:03:41 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Questions about Square Coils
  • I had a picture of JMOR's coil test circuit but can't find it. I believe the 6V front mount square can coil should read 1.3-1.5 static measuring pigtail to top terminal post. FWIW: A 12V coil should read about double that reading. Make sure your VOM is set to the RESISTANCE (OHMS) scale. Polarity doesn't matter. That being said, I also believe that test doesn't necessarily mean the coil is good. Once it gets hot, it can fail and short out. Additionally, from what I've been taught, if the key switch was left on at some point, and the pints were closed, the coil could possibly melt the internal tar insulation thus creating the short. Once it cools down, the coil may work but as soon as it gets hot again, it loses its insulating ability and shorts out. I have a box of old coils, some OEM with the FORD script on top. Last summer when I did a tune-up on my '48 8N, I was tightening the coil terminal post nut and snapped off the stud off. I tested an old used coil from my box, had 1.5 reading on it, installed it, and it worked fine and is still on the distributor. I know you have a solution for snapping off studs too with a quick disconnect tab. Here are some pix of a fixture I made for you to secure the distributor while doing a tune-up. I'll bring this with me as well next visit.


    Tim Daley(MI)

    Tim Daley(MI)    Posted 12-04-2018 at 05:29:52 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Questions about Square Coils
  • Dan-
    Your Front Mount Test Gauge I modified...


    I will return it next time I visit.


    Farmer Dan    Posted 12-04-2018 at 08:29:24 [URL] [DELETE]        [Reply] [Email]  
  • Re: Questions about Square Coils
  • No need Tim, I am designing a new one. Just need someone to build it for me LOL.

    K.LaRue-VA    Posted 12-03-2018 at 21:49:25 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Questions about Square Coils
  • I agree with the suggestion to just swap any questionable coil onto a tractor that was running fine and see how it works for a few days (then label each coil "good" "bad"). It's impossible for any bench measurement or test rig to duplicate normal operating conditions with heat, vibration, wind, moisture.... The time it takes to flip a bail and swap one wire connection is a lot less than it takes to build a test rig.


    Farmer Dan    Posted 12-04-2018 at 08:25:32 [URL] [DELETE]        [Reply] [Email]  
  • Re: Questions about Square Coils
  • Due to my new health limitiations I can't work on the tractor anymore. Plus JMOR is right I like to play at my work bench/dinning room table.

    JMOR    Posted 12-03-2018 at 22:21:33 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Questions about Square Coils
  • true enough, but Dan likes to play. :)

    JMOR    Posted 12-03-2018 at 20:37:28 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Questions about Square Coils
  • for small resistances, I have much better test/measurement results by applying a measured current (1 amp is good) and then using a different than ammeter (leaving ammeter in circuit so as not to disturb measured current) to measure coil primary voltage and calculate resistance with V/I.
    Imgur is not permitting uploads, so I will send you a buzzer/relay circuit that can be used to make the coil spark at relatively high rate, via e-mail.

    HCooke    Posted 12-03-2018 at 17:57:51 [URL] [DELETE]        [Reply] [Email]  
  • Re: Questions about Square Coils
  • Short of that testor you made, the next best would be putting them in Maude and see if she likes the,

    Tony C    Posted 12-04-2018 at 11:46:37 [URL] [DELETE]        [Reply] [No Email]  
  • Re: Questions about Square Coils
  • If I didn't have a SNAP-ON MT 335 coil tester, HCookes' solution would be my first choice.

    Tester is very easy to use on or off the vehicle. Just a couple of hook ups. It also has a heating circuit to test for heat related open circuits.

    Last one I saw listed went for $55.

    Dave Smith    Posted 12-03-2018 at 17:56:59 [URL] [DELETE]        [Reply] [Email]  
  • Re: Questions about Square Coils
  • If the coils have the Ford logo on them they are
    definitely worth money. Some of the old flathead
    V8 coils with logo bring up to $80 for a core.
    Dave <*)))><

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