[villagetinker]

Originally Posted by dougawhite

I changed out from a tank heater last year; seemed like a good deal from TECO with monthly no-interest payments. Right away, a couple times per month, the shower would go cold. Turned the faucet off and waiting for everything to heat up again and got hot water again. Thought it might be the shower valve, but then it started happening in our other shower. Finally had original installation plumber check it out and they agreed with me there was probably something amiss with the main circuit board, but the manufacturer said they would not agree with this part replacement. So the plumber left and again today the shower went cold. Has anyone else had this negative experience with a tankless water heater?

As I recall TECO is both a gas and electric company, so is the tankless water heater a gas or electric unit? I am GUESSING that the unit maybe cycling due to an overtemperature condition. Try an internet search on you make and model to see if others have reported the problem and any possible solutions.