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  1. #1
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    2021 25G Fuel Gauges Not Working

    Hello all,

    Hoping someone can help me with what I think is a new fuel gauge issue. My new 25G fuel gauges weren’t working so I thought it was missing the power wire per the 2019 service bulletin. Took the panel apart this weekend and the analogue gauge inside had wires to the +, - and S terminals.

    Tried swapping the positive and negative wires and all it did was peg the gauges on full.

    From the factory I have nether the inside (control panel) or outside (next to pump) gauges working.

    They are missing signal some how. Any help is appreciated!

    Jim

  2. #2
    Commercial Member huntr70's Avatar
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    The signal comes out of the tank sending unit, into the exterior gauges, then passes in to the inside.

    I would check at the pump gauges and look for loose wires.
    Steve- Inventory Manager at Tom Schaeffer's RV, Shoemakersville, PA www.tomschaeffers.com
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    2011 RAM 3500 SRW Outdoorsman Edition 4X4, 6.7 Cummins--TWEAKED!
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  3. #3
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    Quote Originally Posted by JamesKGoff View Post
    Hello all,

    Hoping someone can help me with what I think is a new fuel gauge issue. My new 25G fuel gauges weren’t working so I thought it was missing the power wire per the 2019 service bulletin. Took the panel apart this weekend and the analogue gauge inside had wires to the +, - and S terminals.

    Tried swapping the positive and negative wires and all it did was peg the gauges on full.

    From the factory I have nether the inside (control panel) or outside (next to pump) gauges working.

    They are missing signal some how. Any help is appreciated!

    Jim
    @JamesKGoff were you ever able to get this figured out? I'm experiencing the same thing and I have hit dead ends with everything I've tried.

  4. #4
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    I have not, but taking it away next week and plan on playing with it. Any chance you can share what you tried?

  5. #5
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    Quote Originally Posted by JamesKGoff View Post
    I have not, but taking it away next week and plan on playing with it. Any chance you can share what you tried?
    Sure - here's what I've done so far - each step was isolated by itself so I could see what item would actually fix it. None of them have worked

    1. Traced the (+) from the fuel gauge to make sure it's going to a (+) in the trailer (confirmed)
    1a. Moved the (+) from where it connected to the trailer to a different constant power connector (the one the specified in the TSB)
    2. Traced the (-) from the fuel gauge to make sure it's going to a (-) in the trailer (confirmed)
    3. Went to the back of the trailer to the fuel tank outside and found the brown wire that comes out of the analogue gauge and re-did the connection back there (it was a crappy crimp connection and I replaced it with a good wire nut)
    4. Flipped the (+) and (-) like you did to make sure the gauge would peg to full (to make sure a sensor wasn't stuck in the gauge)
    5. Disconnected the white/yellow (-) wire from the back of the fuel gauge (but left the blue one there) to make everything 100% match the TSB that was put out (no change)
    6. Pulled out the "fuel pump" fuse from the fuse panel - went back and checked the gauge and it was pegged on "FULL" - put the fuse back in and the needle returned to empty.


    I'm pretty much at a loss for where to go now. It seems like the signal just isn't getting sent from the tank sensor itself. Like maybe the brown wire from the digital gauge at the tank may be severed somewhere along the way.. My next steps are going to be to get an ohm meter and check the power readings for each wire. I found a thread somewhere that said what they should be, but I'll have to dig it up when I'm checking it.

    I called GD and they weren't very helpful - to their credit, I wasn't physically in the trailer at the time and they said they'd only help if I was physically at the trailer, with an ohm meter in hand, and I "expressed the desire to self troubleshoot" (gotta be some sort of legal language that frees them from liability haha)

    Anyway - if you're able to figure it out before I do, I'm all ears!

  6. #6
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    Cooper,

    I did it. Got the wiring diagram from ECI. Grand Design wired both the sending unit AND the inside fuel gauge wrong!

    On the inside fuel gauge I had a brown wire connected to S, white and yellow wire connected to positive and blue wire connected to negative.

    When we checked for DC voltage on the wires as connected, nothing. Digging around the cabinet we found the blue is not a negative. We kept the white/yellow to the +, hooked up the white we found (paired) to the white/yellow to the negative and fixed the inside.

    The outside was another issue. The sending unit has three two prong connections. Two stacked on top of each other to the left of the 4 prong power connector. One under the four prong connector (with connector and no wire). The black and white (level sensor from tank was on the bottom of the stacked connection points and single black signal connector (connected to brown wire) on top. Those positions need to be swapped!

    Then ECI said to connect the signal and level sensor wires before turning on power and connecting the 4 prong connector. WORKED!

    Hope this helps.
    Last edited by Second Chance; 04-06-2023 at 04:32 PM.

  7. #7
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    Daaaang dude! That's awesome!

    So in summary:

    - The Inside Fuel Gauge you now have a positive wire hooked up to a positive (Yellow/White), a negative wire hooked up to the negative post (White/Yellow), and the brown wire hooked up to the S. Correct? You just disconnected the Blue wire and left it hanging in your cabinet?

    - On the outside, I'm not really following what you're saying... Do you think you could take a picture of the wires as they should be and post it? Or could you post the ECI Wiring Diagram? Sorry to be a pain, but I think this is where my problem lies and I'm super excited that you've figured out how to fix it.

    You the man! I really really appreciate the follow-up brother!

  8. #8
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    Hey Jeff,

    Thanks for all your help! Mine were hooked up a little differently then yours, but I've attached a picture of what the outside sending wiring needs to be.

    Click image for larger version. 

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    After these were hooked up correctly I just had to un-plug and re-plug in the trailer and we were good to go!

  9. #9
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    Great news! The only other thing I discovered is the gauge inside won’t work while shore power is to the rv. Guess that makes sense as you don’t need gas for geny with shore power. When off shore power and back on 12v the gauge works again.

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