Quantcast COIL POLARITY

Order this information in Print

Order this information on CD-ROM

Download in PDF Format

     

Click here to make tpub.com your Home Page

Page Title: COIL POLARITY
Back | Up | Next

Click here for a printable version

Google


Web
www.tpub.com

Home


   
Information Categories
.... Administration
Advancement
Aerographer
Automotive
Aviation
Combat
Construction
Diving
Draftsman
Engineering
Electronics
Food and Cooking
Math
Medical
Music
Nuclear Fundamentals
Photography
Religion
USMC
   
Products
  Educational CD-ROM's
Printed Manuals
Downloadable Books
   

 

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Back
COIL SERVICE
Up
TM-5-4210-230-14P-1 Aerial Ladder Fire Fighting Truck Manual
Next
CONDENSERS
TRUCK SERVICE MANUAL TM 5-4210-230-14&P-1 ELECTRICAL Fig. 4 Schematic Diagram of Primary and Secondary Circuits of 12-Volt Ignition System obtain greatly improved starting performance at low temperatures,    the    resistor    is    bypassed    during    cranking, thereby   connecting   ignition   coil   directly   to   battery.      This makes  full  battery  voltage  available  to  coil  and,  thus,  keeps ignition  voltage  as  high  as  possible  during  cranking.    The bypassing of ignition resistor during cranking is accomplished by use of a "finger" within the solenoid which is connected to the ignition coil.  As solenoid contacts close, the ignition coil is connected to battery through the solenoid "finger".  To prevent the engine from firing while making underhood cranking tests on   trucks   using   12-volt   system,   ground   distributor   primary lead. COIL POLARITY One of the major causes for hard starting or spark plug misfiring under load results when the ignition coil lead wire to the distributor is installed on the wrong side of the coil.  This condition causes reversed coil polarity. Voltage  at  the  spark  plug  terminals  should  always  be negative.    Whether  it  is  or  not  depends  on  how  the  primary leads are attached to the coil.  Remember, primary lead hook- up   directly   affects   coil   polarity,   which   in   turn   determines whether  voltage  at  the  spark  plug  terminals  is  negative  or positive.    On  IH  trucks  the  distributor  wire  to  the  coil  should always   be   placed   on   the   negative   side   of   the   coil   if   the electrical system is negative grounded, or on the positive side if the electrical system is positive grounded. If  the  primary  leads  are  incorrectly  attached,  the  direction  of current  flow  through  the  coil  is  reversed.    Consequently,  coil polarity    is    reversed,    resulting    in    positive    voltage    being supplied to the spark plug terminals. What   difference   does   it   make   whether   positive   or negative  voltage  is  supplied  to  the  spark  plug  terminals?.    It directly affects the amount of voltage required to fire the spark plugs.  When polarity at the spark plug terminals is positive, it's  harder  for  the  voltage  to  jump  across  the  air  gap  than when polarity at the plug terminal is negative.  Just why this is so is related to a pair of electrical theories--the electron theory and the theory of thermionic emission. According to the electron theory, all current flows from negative to positive.  The theory of thermionic emission states essentially it's easier for electrons to leave a hot surface than a cold surface. Combining  the  two  theories,  one  finds  that  electrons will  always  leave  a  negative  charged  surface  for  a  positive charged  surface,  and  they  will  leave  the  negatively  charged surface with more ease when the surface is heated. Spark   plug   design   is   such   that   the   center   electrode almost   always   operates   at   a   higher   temperature   than   the ground electrode.  Since it's easier for electrons to leave a hot surface,  it  is  preferred  to  have  the  electrons  "jump"  from  the hotter center electrode to the cooler ground electrode. When    the    center    electrode    is    negatively    charged (negative  voltage  at  the  spark  plug  terminals),  this  is  what happens.  Stated another way, putting the negative charge on the  hotter  center  electrode  causes  the  gap  to  be  ionized  at lower  voltage.    (Ionization  is  necessary  to  permit  passage  of the   spark   through   the   high   resistance   of   the   gases   in   the cylinder.) When positive voltage is supplied to the plug terminals, which happens when coil polarity is accidentally reversed, the hotter center electrode becomes positive charged. Consequently,   electrons   must   leave   the   negative   charged ground  electrode  and  move  to  the  positive  charged  center electrode.  But, since the ground electrode is cooler than the center electrode (and remember, it's easier for the electrons to leave  a  hotter  surface),  it  takes  more  voltage  to  make  the current jump the gap-in fact, up to 45 percent more.  See Fig. 5. CTS-2013-E  Page 5 PRINTED IN UNITED STATES OF AMERICA

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing

Integrated Publishing, Inc.