On the outside of most rigs above the wet-bay is usually found a “utility light”. This is handy for hooking up at a campground at night. Some of the older rigs have very inadequate lights for this purpose so I changed mine out for a bright LED solution that provides a surprising amount of light to help you get connected.
To turn this light on and off there is usually a switch on or near the dashboard. In my case, the switch has a light icon.
Under the Hood
What you may not realize is that this switch also turns on and off a light under the hood in the engine compartment. Many rigs may have a burnt out bulb here and, without knowing it exists, may never realize it has this ability. The light is located (in my case) way up above the engine in a very difficult place to reach.
Not all years are the same and some switches and lights may be located in alternate locations, but from what I have read, for the most part, this should get you started on your treasure hunt!