Re: Dsi flt light
It will only come on when it needs to light the propane flame for the water heater. You will see it come on when you first flip the switch for the water heater and it will stay on until the heater fires. Sometimes it will give you the "fault" light if it does not fire right away but it will try again until it lights. If it gives you a solid fault light for a long period of time, check your propane to be sure it is on and not empty.
Basically it is telling you that the electronic spark is firing to light the propane.
I should add that this is something different from the 120 V electric heater switch. It only relates to the propane fired heat.