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4x4 no light and switch doesn't work

Discussion in '7.3L Powerstroke Diesels' started by 90f250, Sep 28, 2019.

  1. 90f250

    90f250 Full Access Member

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    First off, it's been a long time since I've been on here. So long time no see!. Ok so the problem here is: when I bought the truck, some rigged a toggle switch for the 4x4 selector. I re ran the wires back to the switch plug per the wiring diagram I found. They ran the new wires all the way to the g.e.m. I had to splice everything back together the correct way from the factory and I went ahead and replaced the 4x4 switch itself. I've replaced ALL the relays, I've checked every single fuse and all the wiring itself as well. The 4x4 motor works just fine also. I've even taken out the gem and took it apart to check for any corrosion or burnt spots or anything. Every single thing checks out just fine and nothing smells burnt or anything. Now, this being said. The 4x4 light on the dash doesn't come on when I first turn the key or any other time. The switch has no power going to it. But I popped the tops off the relays and manually switched them and the 4x4 motor turns it into 4x4 and back to 2wd when I do the correct relay. So.. my question.. what am I missing that would keep the light from working and keep the 4x4 knob from working?? Also.. the light worked when it was on a toggle switch. This thing is getting aggravating. The truck is an early 99 f250 super duty ext cab short bed 7.3 pstroke with 272k. Thank you in advance! And yes I've searched forum after forum thread after thread and tried everyone's ideas to no avail.
     
  2. 90f250

    90f250 Full Access Member

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    Update: I found a fuse that wasnt even in the fuse block that should have been. Put one in it. I now have power to the selector switch but it still doesn't light up the light or switch Into 4x4.
     
  3. 90f250

    90f250 Full Access Member

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    Still havent figured out this issue and its snowing now! Please help!
     
  4. 79jasper

    79jasper Chickenhawk

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    Should have left it alone. Lol
    I would try swapping the GEM.

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  5. 90f250

    90f250 Full Access Member

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    Yea I know now, lol. I figure it probly is the gem but I dont have 500+ for a new one
     
  6. 79jasper

    79jasper Chickenhawk

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    I can't remember if you can swap one from a junkyard.

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  7. trackspeeder

    trackspeeder Stone crusher.

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    The GEM has to be the same as the original.
    The only way to do this is to make sure the donor has the same options as the original truck.
     
  8. greenskeeper

    greenskeeper Full Access Member

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    Can you manually put the t-case into 4wd. Leave it that way and then manually lock the hubs when you need 4wd? Unlocking the hubs would allow 2wd operation even if the t-case is still in 4wd. That should get you by until you fix the problem. I’m just guessing as I have the old timey manual hubs and t case lever.
     
  9. DaveBen

    DaveBen Supporting Member Supporting Member

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    I have owned a 4X4 Ford truck every year since 1972 and none of them has had SOTF. I have had Manual Transfer cases and hubs. Keep it simple.
     
  10. 90f250

    90f250 Full Access Member

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    Update. Not new but good used gem put it. I matched the numbers on everything before I bought it. Still no dice. I'm back to square one and I suppose I will be tracing every single wire. I prefer floor shifter simply because of this reason. Electronics fail. Yes i can put it in 4x4 manually and just lock in the hubs when needed but I'm really trying to just fix the issue all together.
     
  11. 90f250

    90f250 Full Access Member

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    Anyone have the 99 f250 4x4 esof wiring diagram handy?
     
  12. 90f250

    90f250 Full Access Member

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    Another update. I have 12v at 2 pins in both relays no matter key on or off. Am I wrong in thinking it was only supposed to have one 12v hot all time and then the other when key is on??
     
  13. 79jasper

    79jasper Chickenhawk

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    Depends.
    I know the gems stay powered up for awhile.
    I can't say which features though.

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  14. 79jasper

    79jasper Chickenhawk

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    If you have a good code scanner that will communicate with these trucks, have you tried pulling the codes?

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  15. 90f250

    90f250 Full Access Member

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    It doesn't pull up anything. I just used one the other day
     

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