The water pump switch on my Wildcat 295RSX has always lit up when the switch is on.
The water heater switch for propane DID NOT light up - burned up some propane while sitting in the trailer shed because we didn't notice the switch had been bumped. I knew the switch had a bulb in it. All I needed to do was get it to light up. I pulled the switch and found it had 3 terminals -- 1 was the pos. input to the switch & appliance. 2 was neg. output from the switch to the heater control board. 3 was neg. output for the bulb in the switch. It had no ground (neg.) wire on it so I added one. Now when I flip the switch, its little light bulb comes on and stays on until I turn off the switch.
Don't confuse the light in this switch with the red fault light which stays on UNTIL the unit's burner lights then goes off. (Of course, it stays on if the heater doesn't light.)
The water heater switch if it is a surburban is only for ign or fault others are different. If the water pump one doesn't work possibly the wire is hooked up for the light is connected wrong or not hooked up at all or light is bad. Mine has always worked.
2001 Ford F-350 DRW 7.3
2011 25 RL Wildcat
former fiver 1976 Fourwinds had for 35 years