Attach the sonar sensor plug to the display. Turn the unit on, and place the bottom of the transducer up to your ear. Do you hear a ticking sound? If no, replace the batteries with a new set, and try again. If you still do not hear the ticking sound, and you are operating the unit as per the instruction manual, then the unit may need to be bench tested. Please contact customer service with the production date code (a 3 or 4 digit number on a sticker on the back or bottom of the unit or inside the battery compartment) . If you do hear ticking, you need to retest the unit in water that you know is between within the operating specs of the unit, verifying before you put the transducer in the water that you hear the ticking sound. Keep in mind that extremely dirty water or very soft bottom may cause the unit to display "---". Under these circumstances you should discontinue use of the unit.