a problem with a variable capacitor?

Dear,

The variable capacitor is made of two plates seperated by an insulator. Two legs enough you use in circuit. But whereas design of circuits the three legs are usefull.

Two legs are from one conductor and one leg is another one conductor. I think you have trimmer capacitor for variable capacitance in circuit ( maybe an variable oscillator circuit ).

Try it with continuity tester ( multimeter ) which two legs are same and another one is are other. 1 marked in red may be single leg. You use this in circuit two legs are one connection point, and another one leg is another one connection point.

i.e. :- look this therfore sign. The two dots are one terminal and hyphen indicates ( 1 marked in red ) one terminal.

Note: Use only special tuning tool while tune or test in circuit function.