I had an older one (2004) that started doing that. The problem was intermittent at first, but eventually it quit reading depth all together. I ended up replacing the unit. I tried a different transducer and the problem remained. Which led me to believe the problem was in the unit itself. Since it was 10 years old, I just replaced it.13 PIV w/ 200 MercIG: WarriorRiverCustomRods