No 31C listed but I see in other posts, you have mentioned a 31K?
But the idea for most is the same. Step one is finding the small plate with the tiny button to turn on the amp! Step two is is setting the TV to pick up over the air/antenna signals. this has to be done , often using the remote and going tot he TV settings. Many require a scan to be run to let the TV find what channels are bing picked up.
Each TV builder may do it somewhat different on settings. Kind of like much of the modern gizmos we have and we have to just fight and fuss with it until we are ready to go out and shoot somebody?
The guy that built it has no idea he may be the only one who knows how to do things!
But on an RV that somebody else has owned there may be other pointsto consider as many people do add/remove parts to suit what they wanted and leave the cables disconnected at various points!
So look at this drawing sheet 2 for how it should have been built as a first thought.
check sheet 2 right side for a drawing of the outlet plate from the back side. Note the cable to get cable service or when we turn the amp switch on, it should give over the air channels. Get the light to come on at this plate, showing amp on! Then the cable from here may have been disconnected att eht TV, etc. if the former owner only played DVD, etc. that did not use the over the air!
That can get to be a search to find where it is cut off!
Note the colors marked on the drawings for the cables> Those can help to find tape markers at each end to ID them somewhat!
