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Q: After fill-up, gauge went to top, then dropped to middle and stuck there

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The last time I filled up my Mazda, the gauge went all the way to top about 15 minutes after fill-up and then after driving about an hour, it dropped to middle and stuck there. How do I fix this?

A: The fuel sending unit inside the fuel tank ...

The fuel sending unit inside the fuel tank uses a variable resistor unit to control the fuel gauge. If the sending unit is faulty then it could fail in any position, causing the gauge to not work correctly. A true test is to remove the sender and check the resistance of the sender while moving the float up and down. If it does not match the specification, then it should be replaced.

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