Red "Reset" light on the water heater switch?

If you turn on that switch, the red light tells you it's on. There is a second tiny red light also, that is the dsi fault light. It will light up as soon as you press the switch on. It tells you that the igniter is trying to light the water heater. Once the water heater ignites, the tiny light will go out, so you know it lit. Make sure there is water in the h/w tank before turning on. If yout not sure if the h/w tank has water in it, open the emergency pressure release valve and see if water spurts out. The pressure release valve is located outside at the top of the water heater. 

Turning on the hot water tap does NOT prove there is water in the h/w tank. That's why i made sure I told you about the pressure release. You will get water out of the hot water tap even if no water was ever in the water heater. There are bypass valves that in summer, you set them to let water into the h/w tank, and in winter you set it to "bypass" the h/w tank so no water goes in. Water will still come from the hot water tap even if no water is in the h/w tank, and you will damage the unit. 

Okay i guess i've been just lucky so far. Next time I'll use the pressure relief valve to insure i know water is in the tank. I've seen it done on youtube and it just looks messy- LOL.