1982 308 intermittent fuel gauge operation

When my 308 is cold, the fuel guage seems to work fine, but after the car has run for a while, the gauge pops back and forth between a reading and zero. Then as the engine heats up, the fuel gauge stays pegged at zero.

I have cleaned the contacts at the sending unit, but would appreciate knowing if anyone else has had this problem, or would have any suggestions as to what I need to eliminate as possible causes of this abnormality. For example, can I test the sending unit without removing it from the fuel tank?

 

Thanks for the reply. I'll have it checked.