Fuel Gauge

Any AP out there want to tackle fuel system issue? Right tank is constantly reading full on gauge. Electronic gauge installed in 08/2008. Any help appreciated. BTW - I posted on social media, so I've heard all the "never run out of gas" humor.

Aircraft is at KCCB.


1965 PA-28-180C

~Live life as if everything is rigged in your favor.


  • edited November 2022


    Could be a few different things. Are your sending units the float type? If yes, the problem could be as simple as a stuck float.

    If not, the fault will generally fall into the following categories:

    1. Sending unit is bad. Replacement requires fuel tank removal.
    2. Instrument is bad.
    3. Wiring.

    Swap the inputs on the gauge from the L and R tanks. If the problem switches tank (L tank shows full), then it's the sending unit or a wiring problem. If after switching inputs, the R tank still shows full, then it's either the instrument or a wiring problem.

    Did it happen all at once, or did it occur slowly over time?

    Jim "Doc Griff" Griffin
    PA28 - 161
    Chicago area

  • The early Aerospace units , at least in our experience, were a bit trouble prone. Probe swap sure a good try, perhaps OEM can give you some readings to test the unit itself.


  • @griff390 It seemed to happen all at once. Thanks for the advice. I'll swap wires this weekend.

    @planewrench I tried contacting Aerospace and they never got back to me. On start-up it's running through all the checks correctly according to the manual.


    1965 PA-28-180C

    ~Live life as if everything is rigged in your favor.

  • If you can get at the leads on the back of the unit, you can verify the senders,,, Ohm meter to a lead,, then use a coat hanger to move the sender up and down in the tank. A bit creative, but it does work. Compare resistance left and right. That will help you narrow where the error lies.


  • While not probable, could have stuck float at top of tank. Get a mirror and look for it. Of course dont use a lighter for illumination. I have to add that caution ya know! Carl

  • My Jeep has that issue, sending unit went bad. Nothing dropping a 1/4 inch armored steel plate on my head to access the sending unit will not fix. I buy gas more regularly.

    I can see it being an issue in a plane. If not impossible switch inputs, see if the other tank when it reads low will read full, if it does, you will know it is the sending unit. If it does not read full, you will likely have bad lights or the computer that controls them.

    Or, this could be the excuse you need to order that Garmin 6000 you have been wanting. It comes with fuel level, fuel used, distance till empty, the amount you will pay for fuel at your next stop and if your home equity line of credit will cover it or do you need a second mortgage.

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