I bought a 1998 Towlite and I found a couple switches that I am not sure what they are for. The first switch in question is in the bathroom on the back wall it is a factory switch, and the second is on the counter beside the guage for the battery, gray and black tank.

Some Hi-Lo's had a switch in the bath rear wall that will operate the overhead light if the switch on the light is left in the on position. The switch beside the sensor panel is probably for the external cooling fan for the fridge, when it is turned on the fan operates form a thermostat located in the external cooling fins. Check the manuals in the Reference Library, one close to your year will have pics of the switch.