I have 2 320s and the one on the bow quit showing fish as well as it used to. I mainly use it while sitting or with the trolling motor running. I suspected power but the voltage is good. I then though about running a dedicated line to it but thought why should I, it worked fine when new. I ruled out the tansducer by swapping units. Sure enough the console unit showed more fish echoes. Well last W/E I was on Hubbard and the thing worked fine. Has anyone had this happen to them?

fyi, when you are sitting stll you will not see arches. you will see horiztal lines. you have to be moving see arches.

my 480 did the same thing... i used to set my sens. about 82 percent and it showed everything, baitfish balls trees and all. i now have my sensitivity about 97 percent and it doesn't show jack sometimes....it works for a while then it doesn't work...I thought it was my transducer but i am still not sure.

I know about the fish arches. I set the bow finder to Fish ID for that reason. Mine is definitely not the transducer. I learned my lesson on that one a long time ago. I have a transducer for a paper graph that is 20+ years and still works fine. I believe that it is rare that a transducer goes bad. If I suspected one I would definitely test the new one by just dropping over the side before I installed it.

next time your on the water turn off the unit at the console, any see if that helps. you might be running inteference now. you really need turn off the fish id mode. it will give you some false reading.

your unit also could be going bad too. how old is it.

I do turn off the one on the console. The unit is only 2-3 years old. I only use the fish id when anchored.