1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

75 Cj5 Solenoid Question

Discussion in 'Intermediate CJ-5/6/7/8' started by Aaron Kincaid, Apr 23, 2017.

  1. Apr 23, 2017
    Aaron Kincaid

    Aaron Kincaid New Member

    kansas city, MO
    Joined:
    Apr 23, 2017
    Messages:
    2
    DuraSpark01.gif I have a 75 cj5 barn find I picked up a few weeks ago. Has the 258 I-6, with the dreaded prestolite ignition system in it. Going through and upgrading to duraspark system. I know this has been beaten like a dead horse so bear with me. I searched through the threads and couldn't find my specific question. My starter solenoid is remotely mounted on the passenger fender, but it does not have the "I" terminal, only the "S" All the wiring diagrams I am finding show the dual terminal solenoid. Do I need to upgrade the solenoid also? Thanks in advance!
     
  2. Apr 23, 2017
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
    Joined:
    Aug 3, 2003
    Messages:
    9,754
    The 'S' terminal only activates the solenoid, and thus cranks the starter.

    The "I" terminal provides direct full voltage output to boost the coil during cranking only.

    When running (not cranking) the coil voltage is reduced and comes through the resistor circuit.
     
    Aaron Kincaid likes this.
  3. Apr 23, 2017
    Aaron Kincaid

    Aaron Kincaid New Member

    kansas city, MO
    Joined:
    Apr 23, 2017
    Messages:
    2
    Ok, now I get it. My 75 w/prestolite did not have a ballast resistor or resistor wire, therefore I didn't need the I terminal.
    Upgrading to the Duraspark I am adding a ballast resistor and need the I terminal.
    Probably should have put 2 and 2 together.
    Thanks PeteL!
     
  4. Apr 23, 2017
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    Yes, "S" is start and "I" is ignition. I'm adding a little detail, which you may have figured out already:

    As you surmised, the two terminals on the starter solenoid are normally used to bypass the ballast resistor when starting. The Duraspark module also has a feature that retards the spark while starting for easier starts. This is the white/blue wire. As shown in the drawing, the red/red wire branches off ahead of the ballast resistor, so power to the module is not current limited. The ballast resistor limits the current through the coil while the engine is running. This also limits the amount of current the module must sink when switching the coil. You need the ballast resistor with the Duraspark module, or else it will overheat, fail and melt the potting compound all over your inner fender.
     
New Posts