I have the same problem, the control box and well are bone dry, all leads are secure as far as I can make out, so I need to check the sensors I guess.. Having said that however I can strongly recommend checking this thread if you have lost a wallet lately.. Having ransacked the house and checked the car several times a month ago, and having gone through the hassle of cancelling cards, requesting new ones and driving licence photocard etc.. I should have just checked my parking sensors control unit.. I have just found my wallet safe and sound in the well beneath the passenger seat!