Hello mylesjiml,
The Cascade Rapide water heater has two methods of heating its water. Gas and/or mains electric. You can use either or both together as they have dedicated thermostats for each system, and they have two separate control switches.
I am pretty certain from your description you are looking at the gas system control switch, which does not affect the mains heater at all. If the Red light comes on, that suggests the gas burner has failed to ignite and the system has locked out.
The mains powered element will have a domestic style fused spur switch, Some caravan manufacturers used a switch with a Neon and some didn't. To find it, follow the cable from the inboard end or the heaters tank. To use it, simply turn the mains switch on or off as required. If the heater has been empty of water and turned on and over heated, then there is a resetable button on the plastic housing on the inboard end of the heater.
My advice is to read the instruction book for the heater. If you haven't got one look at
arcsystems.biz