Originally Posted by bubbles
Just a comment for Blaster 84. The control panel water heater switch is not illuminated to show that it is on. When you set the switch to on but it will illuminate momentarilly showing that ignition is in progress but will extinguish when all is normal and not illuminate again unless there is an ignition issue. The lighted switch will not be illuminated if the water heater is functioning normally. In otherwards, the switch light is not to indicate the position of the switch. If your holding tank is showing 1/3 full there may not be enough water actually in the tank if your unit is tilted to one side for the pump to prime itself.
I think there can be several type of control panel switches. I do have an illuminated rocker panel switch to show the water heater switch is on (it's a blue light).......that also has another DSI fault light (it's a red light) beside it, that comes on until the propane lights up.
I have another camper that doesn't have an illuminated rocker panel switch, but just a DSI fault light.
On the first one, that has an illuminated rocker panel switch, the switch does stay an illuminated blue the entire time the switch is turned on. It's possible the OP has an illuminated rocker panel switch like this.....with a separate DSI fault light beside it.