89 Lariat fuel gauge issue

Discussion in '1987 - 1991 Ford F150, F250 and F350 Truck Forum' started by BigBen302, Aug 30, 2020.

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  1. BigBen302

    I recently picked up the truck and fuel switch for dual tanks works, but the gauge always stays pegged to the F so I never know how much gas I actually have. What is the cause? Is it an easy fix?
     
    BigBen302, Aug 30, 2020
    #1
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  2. FTZ HAIC Staff Member Oregon Chapter Founding Member

    If it's reading full all the time it means the guage is getting 0 ohms, which usually means there's a short to ground.

    If it happens with both tanks, the short is between the gauge and the tank selector switch. If it happens only with one tank, then it's between the switch and the sending unit at the tank.
     
    Last edited: Sep 6, 2020
    FTZ HAIC, Sep 3, 2020
    #2
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  3. BigBen302

    I will check that out. That would be an easy fix if that's all it is. Thanks!
     
    BigBen302, Sep 5, 2020
    #3

  4. Marlon

    Hi, i just bought the same truck and my gauge works. But it works all the time still with the ignition switch off. Is that normal?
     
    Marlon, Mar 29, 2021
    #4

  5. Mike’s trucks

    1989 F250 lariat 7.3l Diesel
    Front tank reads empty all the time
    Back take reeds full all the time
    Truck has a parasitic draw 2-3A when the engine is hot and off
    Access to a free wiring diagram would be helpful
     
    Mike’s trucks, Sep 25, 2022
    #5
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