ktw001

hi, bought my 2001 galaxy 7 months ago the parking sensors have never worked, then 2 days ago they started working only for 1 day though, iv done the clicking test 1 rear is not clicking, iv also swapped the sensors around and the one that doesnt click still doesnt click..today it started working again so i pushed the dash button and again done the clicking test this time the sensor was clicking but faintly compared to the others, question is does this just sound like a intimitant sensor fault or could it be something else playing up?? thanks in advance for any advice...