Some times the GPS would work ,then it wouldn't. Same with the fish finder. Then it might be working fine & just go off by itself. I would then have to restart the whole unit from scratch.loosing all my wpts. Each unit had a diff. problem. Even Lowrance support couldn't figure them out. I rerouted the wires, isolated them, did everything Lowrance told me to do. Luckily I took out the extended warranty or I would have been holding my hand on my a$$! After the 4th. one they said "Maybe We have a problem"! & I upgraded to the HDS 7.(which has been around a while longer) as I said I have had good luck with the Hds 7 so far, knock on wood! At any rate I would advise taking the ext. warranty for at least a yr. West marine did the exchanges with no ques. asked but I did explain to them what each unit problem had/did at the time.