!@ volts to coil !!??

Discussion in 'General IH Tech' started by Baker D, Feb 2, 2006.


  1. Baker D

    Baker D Farmall Cub

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    ok i cannot get twelve (or any) volts to my coil, i have a prestolite so from what i can tell i will need the resistor, but cannot get any voltage from the "s" terminal of the starter( the upper post on the starter) i cannot get any volts from the R post (lower) either, when the key is on run, i tried a couple different wiring configs. but still nothing-is my starter toast or what?? i thought the resistor was a resistor wire- circuit 16 in my manual. BTW its a 72 SII 304 727 etc., if I run an ignition hot 12 volt wire to my coil while idling/ driving will i fry it???? Also there is a post on my starter body Not the solenoid that is mid sized( bigger than the s and r and smaller than the B post and i have a green wire in the harness with the correct sized connector, i went ahead and connected them- does any one know what this is-m its not in the wiring diagram or schematic
    BTW i cannot tell which terminal is the "S" or "R" terminal on my starter from the wiring diagram i only know which id the upper and lower when the starter is installed
    Thanks
     
  2. Baker D

    Baker D Farmall Cub

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    sorry, i meant 12 volts to coil!!??
     
  3. 250gibson

    250gibson Binder Driver

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    You wont get any voltage from the bottom(?) post when the key is on run. The post only energizes when the solenoid is activated/starter is turning. The top post is energized by the wire coming form the ignition switch. It should have 12V with the key in start. This is what triggers your solenoid The posts don't put out voltage by themselves. You should also have a wire coming from the harness to the + side of the coil through a resistor/resistance wire that gives you 8V.

    Put a volt meter/test light on the top post and have someone try to start the engine (make sure it is in neutral). If you get voltage to the wire, but the starter doesn't turn, then your solenoid may be in need of fixing. If you don't then you have an ignition switch wiring problem. You don't need to have the engine running to test voltage to the coil. Turn the key on. If you have approx 8V at the + side of the coil, then you are ok
     
  4. Doug Shailor

    Doug Shailor Guest

    Circuit #16 comes from the I1 terminal on the ignition switch and goes to the positive side of the coil. It has nothing to do with the starter solenoid. If you have a point distributor (Prestolite or Holley) then you need a resistance in this #16 circuit. If you have an electronic distributor (Holley or Prestolite) you do not want any resistance in circuit #16.

    The starter solenoid has three terminals (excluding the one connected to the starter). For electronic ignition the "R" terminal is not used. The wiring going to the "S" terminal is circuit #17 and comes from the "S" terminal of the ignition switch. If there is 727 then circuit #17 goes through a relay under the dash on it's way to the "S" terminal of the solenoid.

    If you have a point distributor then you should also have a wire running from the "R" terminal on the solenoid to the coil positive which provides full battery voltage to the coil positive when the solenoid is energized only. This "R" circuit provides full battery voltage to help start the engine. Otherwise the "R" terminal has no voltage. And circuit #16 should have a resistance (special wire or a ballast resister) in the circuit to knock down the voltage to ~8v-9v to save wear and tear on the points.

    On an SV engine (266, 304, 345, 392) the starter solenoid is mounted on the side of the starter so the "R" terminal is at the top and the "S" terminal is on the bottom.


    BTW, you said, "... i have a prestolite so from what i can tell i will need the resistor...". IH used both point type and electronic Prestolite distributors in the SII's so just mentioning the brand is not enough info to know which you have.
     
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  5. Baker D

    Baker D Farmall Cub

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    ok i don't have the resistor wire in my harness so i guess that my old dist. was an electronic type, and from the cranking and catching but not running unless i am cranking it with the starter, it sounds like the dist. that came with my "new" engine is a point type and needs the 8/9 nine volts to the coil to run correctly- does that sound right
     
  6. Doug Shailor

    Doug Shailor Guest

    That is an assumption and is not good to do that at any time. You never know what some PO has swapped in or changed. A '72 did not originally come with an electronic distributor. You need to pull the cap off and look inside to see if it has points or not.

    No way we can tell from that description. Again pull the cap off and look.
     
  7. George Womack

    George Womack Y-Block King

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    Re: 12 volts to coil !!??

    Only if the truck is upside down! :eek:

    The S terminal is on top and the R terminal is on the bottom. Same goes for the 4-cylinder engines.
     
  8. Doug Shailor

    Doug Shailor Guest

    Re: 12 volts to coil !!??

    You mean you mount the starter on the right side of the engine? I prefer them on the left side. :rolleyes:

    Good catch, George!
     
  9. 250gibson

    250gibson Binder Driver

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    You may not be able to see the resistor in the harness, It may be wrapped really tight. Take off the cap, as suggested, and look to see if you have points or electronic ignition.

    What kind of voltage do you get at the + coil terminal with the key in the on position? The coil will still work the same with 8 or 9 volts as it does with 12, you will just burn your points with a constant 12 volts at the coil.

    If the engine only runs in the cranking position, then it sounds like you are only getting juice to the coil from the R terminal on starting solenoid. When you are not cranking the engine, the R terminal doesn't put out any voltage. You still need a wire from the ignition switch (run position) to the + side of the coil that will go through a resistor (if points) or straight to the coil (if electronic)
     

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