what brand? There should be a reset button, but if you have readings of 0.00 it is on, just not receiving info. Check for growth on the sending units, on the bottom usually at the leading edge of the keel, port or starboard depending on tank locations. The module may be in the engine compartment (lazarette). My Signet MK175 on my 322 does have a problem with algae on the speed impeller when the boat sits all week, a quick dive with a brush or my fingers does the trick. I've also had luck (hit & miss) with a hand towel tied in the middle of a length of line, two people work their way from the bow back to where the transducer is located with the line going under the hull, pulling the line about 1 foot from one to the other, kind of like flossing, and the towel will remove the offending growth from the transducer and impeller. Ed
