Gas gauge doesn't work

most of the time when your gas gauge goes crazy or quits working,it's the fuel sending unit,float arm/switch. it is located in the fuel tank and is part of the fuel pump module assembly,and has to be replaced as the whole unit,which is around $400.00 if you buy it yourself.you could do a test to see if the gas hand will sweep...hold the odometer trip button in,turn key to on,not start.when the test on the panel begins,let go of the trip button,see if the gas hand sweeps with the rest of them.post findings.