I received a heater in the mail today. I'm not sure if the unit is operating correctly. The temp in the tank is 65 degrees. The heater when set at 78 turns on for about 15 seconds and then shuts off and powers back on after a short period of time. I stuck my hand in the tank and felt the heater when the light turns on and it gets super hot. Is this normal for the heater to get so hot that the temp sensor turns it off so quickly? That's a lot of cycling. I thought I read somewhere that the heater stays on until the temp of the water is heated, not the heater.