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The fuel gauge in my car keeps going up and down. I filled my car up and I know it is full. when I turn the car on the gauge says it is full and then after driving for a few minutes it says that its empty. any advice?

Answers from the Automotive Experts

Amanda J. Pierce, MBA Leigh, Sounds like a fuel sending unit is faulty, or the float in the tank is faulty. AJ Pierce

Jennifer Frey, Automotive Service Writer and Technician at AskPatty.com Hi Leigh, I wish I could tell you that there is an easy way to fix this, but you'll probably have to take it to the dealer for diagnosis. Depending on the year of your vehicle, your fuel gauge is either a simple device with a bimetallic strip, (less expensive to fix) or a microprocessor, (more expensive to fix). Your fuel sending unit tells the gauge how much fuel is in the vehicle, and sometimes the electrical connection gets corroded. The sending unit is usually not located in an easily accessible spot, so it's not easy to do yourself and can be dangerous if you aren't an experienced technician. It could be a few different things causing these erratic readings. I recommend getting it properly diagnosed, or if you don't have the cash to do so, there are ways to get by. If you've been driving your vehicle for a while, you probably know how many miles you get on a full tank of gas. Just reset your trip meter every time you fill up and watch the mileage, (my Civic can go about 300 miles before I need to refuel). As long as your Saab is still driving normally, (no idle fluctuations or surging of the vehicle) then I'd say it's ok to wait a while before getting it repaired. Best of luck, Jennifer Frey

Suzanne Grego, Technician at City of Philadelphia Fleet Management Leigh, You may have a wiring problem at the gauge, you could have a bad float or a problem with your slosh module. (The float is what tells the gauge how much fuel is in the tank and the slosh module is what stops the gauge from going up and down when the fuel gets *sloshed* around while driving.) To pinpoint the problem, you'll have to bring your vehicle in to your technician so they can test the components. Suzanne

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