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Technical Coil gets HOT while sitting.

Discussion in 'The Hokey Ass Message Board' started by Gearhead Graphics, Sep 29, 2020.

  1. Gearhead Graphics
    Joined: Oct 4, 2008
    Posts: 3,614

    Gearhead Graphics
    Member
    from Denver Co

    Mallory unilite electronic ignitin distributor and msd flamethrower coil.

    Noticed today while messing with electrical stuff my coil gets super hot while sitting with the key on.
    Is there anything to stop this from happening? Or should I just remove the hot wire from the coil if I'm keeping the key on for a while? Ballast resistor?

    Finishing wiring of the car and testing things, otherwise I wouldn't have ot sitting long periods of time with key on.
     
  2. Never had a Unilite but it seems it act's just like points when key is left on. Remove wire from coil while working and never leave key on during normal use if engine isn't running.
     
    dana barlow and triumph 1 like this.
  3. Wrench97
    Joined: Jan 29, 2020
    Posts: 150

    Wrench97

    If the points are closed it will get warm setting like that.
     
    harpo1313 and clem like this.
  4. goldmountain
    Joined: Jun 12, 2016
    Posts: 2,234

    goldmountain

    Turn the key to the ACC position if you Don't need the engine running.

    Sent from my SM-T350 using The H.A.M.B. mobile app
     

  5. Yep.
    That's how ignitions always have worked.
    Run the engine or switch to ACC. or burn your points, or coil...
    ....or unplug the hot wire.


    Sent from my SM-G981V using The H.A.M.B. mobile app
     
    SlamIam, Driver50x and olscrounger like this.
  6. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 1,305

    Elcohaulic
    Member

    I never leave my ignition "on" without the engine running.. I'm from the points era too.....
     
  7. leadfoot1000
    Joined: Nov 4, 2005
    Posts: 31

    leadfoot1000
    Member

    Same problem with electronic ignition (pertronix). Wired my radio to work only with key on, listed to the radio all day in the garage (with engine off). Burned up the coil. Replaced coil and rewired radio so it works with key off.


    Sent from my iPhone using The H.A.M.B. mobile app
     
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  8. Even in these circumstances, should it be super hot?
     
  9. G-son
    Joined: Dec 19, 2012
    Posts: 666

    G-son
    Member
    from Sweden

    Well... Say it's a coil with a 1 ohm primary coil, fed by 12V. 12V @ 1 ohm gives 12A going through it, 12V*12A gives 144W. A small item producing 144W of heat without any cooling (such as moving air) will become quite hot.
     
    Last edited: Sep 30, 2020
  10. jaw22w
    Joined: Mar 2, 2013
    Posts: 1,069

    jaw22w
    Member
    from Indiana

    I did the same thing. While working on wiring I left the key on. The Pertronix coil got hot enough to pop the top and leak oil everywhere. It also killed the unit under the cap. A call to Pertronix and they replaced the whole thing free. Excellent customer service.
     
    olscrounger likes this.
  11. the-rodster
    Joined: Jul 2, 2003
    Posts: 6,664

    the-rodster
    Member

    Enough to do this....

    coil.jpg
     
  12. Elcohaulic
    Joined: Dec 27, 2017
    Posts: 1,305

    Elcohaulic
    Member

    One thing about low voltage DC, even though you dont get shocked by it you do get burned..
     
  13. Gearhead Graphics
    Joined: Oct 4, 2008
    Posts: 3,614

    Gearhead Graphics
    Member
    from Denver Co

    @G-son I love it when someone comes in with the big science to shut down the doubters!

    T bucket harness, so no accessory switch on the key. Trying to iron out turn signals, but simple enough to disconnect the coil when keeping the key on.
     
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  14. 500caddy
    Joined: Feb 8, 2019
    Posts: 89

    500caddy

  15. flynbrian48
    Joined: Mar 10, 2008
    Posts: 6,610

    flynbrian48
    Member

    Yup. Been there, done that.


    Sent from my iPhone using H.A.M.B.
     
  16. Gearhead Graphics
    Joined: Oct 4, 2008
    Posts: 3,614

    Gearhead Graphics
    Member
    from Denver Co


    electronic ignition, gonna take a lot of bumping
     
  17. 500caddy
    Joined: Feb 8, 2019
    Posts: 89

    500caddy

    Oops missed the electronic part


    Sent from my iPhone using The H.A.M.B. mobile app
     
  18. "Shut down the doubters"? Why are you being dramatic over a question?
     
  19. winduptoy
    Joined: Feb 19, 2013
    Posts: 2,120

    winduptoy
    ALLIANCE MEMBER

    I've got no accessory switch on the '29 A Roadster but I went ahead and put a toggle switch hidden under the dash that kills power to the ignition and fuel pump for this reason as well as thinking it might be a theft deterrent.
    There has been a couple of times I haven't been able to steal my own car.
     
  20. cjtwigt
    Joined: Dec 23, 2017
    Posts: 120

    cjtwigt
    Member




    Sent from my iPhone using The H.A.M.B. mobile app
     
    winduptoy likes this.
  21. You COULD install a hidden anti theft on-off switch to kill power to the ign or coil like many do.
    That way you can stop the heating, plus have a small amount of anti-theft.
    That will keep you from having to rearrange your wiring.

    Sent from my SM-G981V using The H.A.M.B. mobile app
     
  22. Truck64
    Joined: Oct 18, 2015
    Posts: 4,153

    Truck64
    Member
    from Ioway

    With a V8, at idle the ignition coil is "on" about 66% of the time. It's pretty easy to see why they will roast if the engine isn't running, it's basically a dead short. While a point type ignition it might only be 3 or 4 amps through the primary wiring when running it will get really toasty.
     
  23. G-son
    Joined: Dec 19, 2012
    Posts: 666

    G-son
    Member
    from Sweden

    The diffrence is not just that the current is switched off for a large part of the time with the engine running, it also takes time for it to rise from zero to max each time it is switched on. So the actual current and power going into an ignition coil is VERY different when you compare a running engine and a constant flow of current.

    [​IMG]
     
    winduptoy likes this.

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