I have a 2003 Hot Springs Prodigy. After being set up and plugged in for about an hour, and the temperature set to 104, the stainless tubes on the heater do not feel warm to the touch. I can feel that the pump is on, and I can feel the water moving through the heater tubes. Is this normal? Should I let it run longer? I have little/no electrical knowledge and do not know how to go about testing the heater. Any tips would be fantastic, before I blow $300 on a new heater!