Overheating gas gauge circuit???

[Rangergass]

Hi guys,

I know it sounds strange but my gas gauge drops to empty after the engine gets up to op temperature.
Happens faster on hot days, slower or not at all on cold days.
Always works at startup and seems accurate.
I'm pretty sure the tank isn't heating up so must be circuit in dash so thinking I will troubleshoot as outlined by "RayInStl".
Hoping somebody has some insights.

Thanks.

 

[adsm08]

Well the whole tank isn't heating up, but the sender might be.

The fuel gauge circuit is really simple. Power runs through the gauge, down to a resistor card in the tank, and as the float moves it changes the resistance. That resistor and the float are both attached to the pump, which does heat up.

This should be a fairly simple affair to trouble shoot. First time how long it takes the gauge to die. Then get under the bed, unplug the fuel pump, and find the yellow wire in the plug, then ground it. Then turn the key on. The gauge should go to full. Now time it, and if the gauge stays at full longer than the time it normally takes to die your sender is bad. If it dies on cue the gauge is probably the issue.