First check your battery for voltage, needs min of 12 volts to operate properly. Minelab repair center is best place to send it in, but I would make sure it isnt a battery issue first.
I agree TH. If that voltage is 11.....get another battery or check your charger. I highly recommend a lith 3000 with quick/smart charger. I assume the knob you turn it on with doesnt go completely around either. I like Keith....great guy and does very good work.