Check the join first to eliminate water intrusion/corrosion. You can use the multimeter to check the cable to the join but transducers can be a bit tricky. A lot of the smaller transducers read open circuit when they are ok so a multimeter test is never conclusive. Once you have checked the join, plug it all back together if it looks ok and turn the sounder on - when you put your ear to the transducer you should be able to hear it clicking. By turning the gain up and rubbing the face of the transducer you should be able to generate noise on the sounder screen or even bounce an echo off a hard surface if the angles are right.