2003 Buick Lesabre Fuel & Coolant Gauge Only Work if tank is full??

We have a 2003 buick lesabre & for a few months the fuel & coolant gauge only work right after the fuel tank is filled. Does anyone know how this could be fixed? Thanks in advance.

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snipped-for-privacy@gmail.com wrote:

Could be a bad ground at the dash and those two things are grounding through the fuel sender.
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