If that's a mid 70's to early 80's vintage TT, it probably has lights that only work on 120v and other's that only work on 12v. The 120v lights will be your standard 40-60 watt light bulbs.. The 12v lights will look like your vehicles tail lights.
When I was a teen in the mid 70's, we had a 76 vintage TT and that's the way the lights worked in it. No converter at all and it was either you were plugged into 120v or you were on the 12v battery. If you have an INVERTER that takes 12v power and makes it into 120v, that's different. But, it'll drain a 12v battery pretty fast even if it's being charged daily.
The only time the wall plugs worked in that trailer was when you were plugged into 120v.
The propane operated appliances like the fridge, the water heater and the furnace had actual pilot lights that you had to light first and they stayed lit all the time until the actual flame was needed. Well, the fridge just ran off the pilot and it never went out until you turned it off.
I've never heard of of propane lines "plugging up", but the fresh air parts of the system could get plugged by bugs doing their thing in there..
Lots of manual stuff to do with those older trailers to get things to work when it's all working normally, so it could be alot of different things that aren't in sync if it's over 30 years old.
Good luck!
Mitch