Originally Posted by costaricanwannabe
I have a Garmin 198C Sounder chartplotter that came with the boat (a Cal 39) when I bought it in 2006. The depth sounder..........
We are talking Depth and not GPS?
Not that it matter.
I would try some of what already mentioned, first being a borrowed Transducer if possible.
Also, check the "Pins" at the plug, are they nice and clean or green/dull? Then they need cleaned.
Another may be lose connection. Even, if, you wiggled things around. Depending how often we unplug and vibration (Coupled with other factors) the "Pin Holes (Not Pins)" may become lose and need tightened up some. I not say what you do, I have used a pair of Needle-nose Pliers and I have used something sharp like the end of a Test Light. But, I not there to see and not want to say you need to start squeezing on something with pliers when I not see what we doing.
Also, look at the pins! Are they split so you can slide a Feeler Gauge or something thin into them to sread out a little?