AMC RULES 37,141 #1 Posted June 13, 2015 (edited) So, I've read about this coil frying thing before...but, it's the first time it's ever happened to me. Ran the last little bit of fuel out of the 1075 today, to go through and clean/replace it's fuel system...forgot to turn off the key afterwards, then this strange smell, looked over to see it smoking like a chimney. Internally, what is happening that makes them do this? Why doesn't it happen while they're running. Edited June 13, 2015 by Big Show or Bust. Share this post Link to post Share on other sites
953 nut 56,234 #2 Posted June 13, 2015 While it is running the points are opening and closing developing a pulsating DC current flow through the coil, when not running if the points are closed you have a direct short circuit developed through the coil. You will also want to replace the points and condenser. 1 Share this post Link to post Share on other sites
squonk 41,670 #3 Posted June 13, 2015 When it's running power is flowing through the primary circuit but is interrupted by the points and everything is happy. Not running that power is just sitting there so to speak and if there is enough resistance through the points to ground higher current than normal will flow and fry the coil. 1 Share this post Link to post Share on other sites
AMC RULES 37,141 #4 Posted June 14, 2015 Oh...drats! Share this post Link to post Share on other sites
slovinski 42 #5 Posted June 14, 2015 Shucks.....is that the same tractor that was making the whining sound and hard to start? 1 Share this post Link to post Share on other sites
Terry M-(Moderator) 2,177 #6 Posted June 14, 2015 Oh...drats! No Worry Craig....I'll be more than happy to take that tractor off your hands..... 1 Share this post Link to post Share on other sites
AMC RULES 37,141 #7 Posted June 14, 2015 Yep, same tractor... sorry Charlie, new coil is on it's way. Share this post Link to post Share on other sites
Save Old Iron 1,566 #8 Posted June 14, 2015 (edited) Something to consider gentlemen ...The points are always a low resistance connection so this is not part of the explanation.During the time the engine is running , the points are closed about 95% of the time anyway, regardless of how long the tractor runs. Points only open VERY BRIEFLY - a few fractions of a second - every complete ignition cycle to fire the spark plug. Something else is at play beyond point resistance and the few fractions of a second the points remain open every ignition cycle. Something to do with magnetic field strength, saturation, conversion of energy and an electrical property of the coil called inductance.Anyone want to venture a more accurate reason why this extra 5% on time cooks a coil when being on 95% of time doesn't? Edited June 14, 2015 by Save Old Iron 1 Share this post Link to post Share on other sites
AMC RULES 37,141 #9 Posted June 14, 2015 Something told me... SOI was gonna have fun with this. Share this post Link to post Share on other sites
953 nut 56,234 #10 Posted June 14, 2015 I know that SOI will have a much better explanation than mine, but here goes. As I recall it from high school shop class the majority of the current flow while the points are closed is consumed in building a magnetic field and the collapsing field that occurs when the points open opposes the incoming 12 volts. Share this post Link to post Share on other sites
Terry M-(Moderator) 2,177 #11 Posted June 17, 2015 Something told me... SOI was gonna have fun with this. I thought so too craig...Meanwhile I'm sure he's busy listening to the Mrs. Miller collection. Share this post Link to post Share on other sites
Save Old Iron 1,566 #12 Posted June 17, 2015 (edited) Something told me... SOI was gonna have fun with this. I thought so too craig...Meanwhile I'm sure he's busy listening to the Mrs. Miller collection. She is a gift , isn't she?https://www.youtube.com/watch?v=-zKCQK0apKc Edited June 17, 2015 by Save Old Iron Share this post Link to post Share on other sites
Save Old Iron 1,566 #13 Posted June 17, 2015 (edited) the majority of the current flow while the points are closed is consumed in building a magnetic field and the collapsing field that occurs when the points open opposes the incoming 12 volts. Correct sir, but not the full story.What does the coil do with the stored up magnetic energy when the points open? Edited June 17, 2015 by Save Old Iron Share this post Link to post Share on other sites
Save Old Iron 1,566 #14 Posted June 19, 2015 another visual cluearea under the curve is power consumed in the coilorange is when when engine is runningyellow is when engine is not running w/ points closedany difference? Share this post Link to post Share on other sites
AMC RULES 37,141 #15 Posted June 19, 2015 Will someone ask the Squirrel...to please pass me a spoon? Share this post Link to post Share on other sites
dcrage 628 #16 Posted June 19, 2015 Heh Chuck -- What is the definition of "power consumed" -- Does this mean what form of energy the current gets converted to -- I am assuming with the engine running we are talking about the spark -- Engine not running I guess heat is generated (and is heat the correct term here; this seems to be getting off into thermodynamics land) Share this post Link to post Share on other sites
