Sonar not working properly

[WCCT]

I have a Lowrance LMS 330c Gps unit that doesn't seem to be working properly.  The sonar part of it is not reading any thing.  I just get a bunch of clutter.  I have changed all of the settings as far as sensitivity and surface clarity go, but nothing works.  I thought it was interference from my fuse panel, so I went direct to one of my batteries with an inline fuse, but it still does not work.  I also tried changing the angle of my transducer.  Do you think I bought a faulty unit?  Any help would be greatly appreciated.  Thanks in advance.

[Muddpuppy]

If you just bought it I would think faulty unit.  If you have had it a while and it did work alright, I would check out the transducer.  If you have anouther unit just like it on your boat or know somebody that does, swap units or take it and try it useing a different transducer.  It doesn't take much to damage a cable.  LEI or Lowrance may have something about checking one out on their sites.