Diagnosing "No Power to Control"

Discussion in 'Fisher Engineering Discussion' started by cwren2472, Nov 21, 2018.

  1. Philbilly2

    Philbilly2 PlowSite Fanatic
    Messages: 12,081

    @Michael J. Donovan

    Any way you can make this a sticky on western, fisher, even blizzard fourms.

    It would be a huge help to is that are here to solve DD issues.

    Thanks!
     
    Randall Ave and Western1 like this.
  2. Ranger429

    Ranger429 Member
    Messages: 48

    cwren, I have a question for you. On page 6 for the isolation module testing, PORT B-PIN C,
    control Power out; I have no power coming out of my module but you don't list what the next step would be. I ended up running a 12 volt jumper wire there and I have a fully functioning plow. Could it be a bad isolation module?

    I'll give a brief rundown. My plow started to work sporadically the last couple of times I've used it. Hooking my test light up to the positive side of the battery I was checking my grounds. I had the ground at the motor but I also had a ground at the positive cable hooked to the motor. Somewhere my system was grounding out which lead me to your post for testing. While the plow now works with my jumper wire hooked to PIN C I'd like to get it fixed the right way. Thoughts? And thanks for doing this write up. It saved me from calling it a day today.
     
  3. OP
    OP
    cwren2472

    cwren2472 PlowSite Fanatic
    Messages: 7,687

    Which tutorial were you following?

    No power coming out doesn't really tell you anything in and of itself unless you've followed all the other steps to verify that all the conditions are met for power and ground coming in.

    It may seem counter-intuitive but that's normal. The current follows the path through the motor from the positive to the ground on the other side. When the motor isn't being powered, you basically end up with a circuit open on one side and ending at the ground on the other.

    Were the lights switching over correctly prior to jumping that pin? If so, then based on what you've said, it does sound like the module might be bad.
     
    Last edited: Feb 13, 2020
  4. Ranger429

    Ranger429 Member
    Messages: 48

    I was on page 6 for my diagnosis on the link from your very first post. Yes I had power coming into the module for the control harness but no power coming out on PIN C PORT B.


    Appreciate the reply for the clarification for the ground issue at the motor. I was unaware of that.

    yes my headlights worked as they should
    And switched over to the plow lights when plugged in.

    77B8B70C-7732-48B7-8568-0EEBD2920CF5.png

    B4127085-6775-4AF2-B6EA-F48440EF97F4.png
     
  5. OP
    OP
    cwren2472

    cwren2472 PlowSite Fanatic
    Messages: 7,687

    Perhaps it wasn't clear, but if you don't have power at PORT B, PIN C, you just continue to the next line (control power IN)
     
  6. Ranger429

    Ranger429 Member
    Messages: 48

    Ah yes I thought I posted this but didn’t. I do have power in for controller.
     
  7. Ranger429

    Ranger429 Member
    Messages: 48

    Answered above, did you have any ideas on this?
     
  8. OP
    OP
    cwren2472

    cwren2472 PlowSite Fanatic
    Messages: 7,687

    Sorry, I didn't realize you were looking for an answer. Based on what you said, it does sound like the module is bad. The way you spliced it already would be the fix or you'd have to swap out the module with a new one (or take it to a dealer to have them bench test it and confirm it's bad.)
     
    Ranger429 likes this.
  9. Ranger429

    Ranger429 Member
    Messages: 48

    I’ll pull it and have it tested. Thanks for the reply.