It is always hard to say what a previous owner has done with the wiring on a trailer. Yours may not have had a standard "Bargman type" flat pin connector when it came out of the factory, AS used a round pin system for many years, and I don't know when they changed to the more common type. In addition, the common color codes used for the Bargman type connector were not the same as those used on the AS when they used the other round connector system.
The first thing to do, however, is to spray some contact cleaner (Radio shack or some auto parts places) into the TV connector as well as the AS connector, and insert and remove the plug half a dozen times. Often that alone will clean up the contacts and things will begin to work.
If that does not solve the problem, you will need to identify which wires do what on the plug from the AS.
One way you might test things is this: With a good battery in the AS, or the unit plugged in to 120 volt power so the converter/charger is running, take a meter and ground one of the meter wires (usually the black one) to the AS frame. Then touch the probe of the other meter wire to each of the flat pins in the connector until you find the one which has 12 volts on it. Make a diagram so you can find it again.
Now, this next part is tricky and critical. One of the other pins will be grounded, and all the remaining ones will operate something, like lights. It is hard to identify the grounded pin with a meter. I know this sounds strange, but if you go to an auto store, buy a fuse holder and several 15 amp fuses you can safely identify the remaining pins.
Put one lead of the fuseholder into the 12 volt
pin you identified above. Touch the other to any other pin. One of two things will happen: either a light will come on on the trailer (running lights, left turn, right turn or backup lights) or the fuse will blow. If you see a light working, note the pin and the light. If you blow the fuse, you have found the ground pin. Replace the fuse, and don't touch that pin again. Go on to each other pin and identify which lights they operate. One pin will not operate lights, or blow the fuse, but it may spark when touched. That will be the electric brake circuit.
Now, this all assumes that the running lights, brake lights and backup lights are working properly. The probability is that some of them at least are operational, and this test will identify those which are working at least. Once you know what pins and circuits are working, you can repair the remainder, or re configure the plug to the normal configuration that is the industry (Bargman) standard.
Other than that, taking it to an RV repair facility is the other option. That only costs $$ something you will be spending anyway on an older AS....grin
Best of luck, and hope this helps.