Hey Frank...Tell this guy to do a master reset on the unit. This is done by
holding BOTH the left and right key while the sounder id off. Then switch it
on while still pressing the arrow keys. The sounder will go into a reset
mode and have a grid on the screen. After 30 seconds or so, switch it off
again, then start it as normal. That may fix it.
Also tell him to check that there is no crap stuck to the base of the
transducer. If it is dirty, just clean it with warm sopy water. Dont try any
harsh cleaning chemicals, or try and scrape it clean as it may get
scratched!
The big Fella