sonar problems

[wkillette]

I have two Garmin units on my boat. One sonar/GPS combo (178C) and one sonar only (320C). The two transducers are mounted on the opposite sides of the transom. The 178C has a constant clicking sound, the other is silent. I have not heard the clicking before. I just added the 320C to the boat. (It was recovered from my stolen boat – another story). Periodically I get a screen full of light diagonal lines, I can still see the sonar image in the back. If I turn the 178C off the lines stop. I can not link the lines to any radio usage.

What is your views, is the 178C transducer failing/failed or is this just transducer interference? If interference, how do I stop it other than removing one?