inverting a signal

[scoobie_wrc]

long story short,

ive put an instrument panel from a newer model into my car, everything works fine except the fuel guage.

when i fill it up it reads empty, when its empty it reads full, etc

so i need to invert the signel before it gets to the panel, so how do you invert a signal?

anyone help?

 

[scoobie_wrc]

the cars a mk3 fiesta, the clocks are from a mk5, there's only 1 wire for the guage m8 so cant swap

 

[scoobie_wrc]

not sure if the sender will fit m8 tank,

give it ago though, cheers guys