need help gas gauge doesn't work

[omgherb]

as title say my gauge cluster gas gauge doesnt read accurately and i would fill the tank up and it will only read to a little after half tank and ever had this problem and if so how can i fix it

 

[LiEkjAi]

could be the green film behind the cluster? or something loose? or the pin is wack.. try taking out the cluster and look around