GSD21 Question

[MH321]

I have a Gsd21 with a 2010 plotter. I was haveing trouble with my transducer cutting out at 500ft. I talked to airmar and they talked me into a M260. They said it would work at the lower wattage on the GSD21 box. I installed it and everything worked fine in the Marina and for about 5 miles out. I was getting a very nice screen. Then it started blinking telling me it isn't reading the bottom. I shut the machine down trying to see if when it came back on it would read and there was only a line no numbers. When I returned to the marina I plugged the old transducer in and it worked. I checked out the install on the Airmar and everything looks good. So I called Airmar that the M260 never goes bad it is probley the GSD21.
When I first installed the M260 I was suprised at how pronounced the ping sound was. When I came back in I couldn't hear it. I pulled the Airmar up out of its box and plugged it in and the thing was pinging but you could barely hear it. I could feel it on the bottom of the transducer. I am in Mexico to send the Airmar back to be ck'd is going to be a pain. Can any one tell me if this is the way the GSD21 will act when it is bad.

[Speckulator]

It sounds like the gsd21 is bad. I have the same thing happen a couple of times and the machine wound stop reading the bottom and showing my water temp., etc. My problem turned out to be that my 3205 unit was actually the problem, as it kept burning up the gsd21s somehow. I could replace the gsd21 and it would work for a while and then go out again. I finally sent the whole unit back and garmin replaced it and I havent had any problem since.