You can repair as Garry indicates. Replacement is a bit of a pain but can be done if you have time (2-4 hrs depending on how familiar you are with wiring type DIY). For the time involved to repair v replace I'd do the replacement. Cost you about $35.
I replaced mine since I fitted a ProPride which needs the extension and I was starting to get intermittent loss of lights/brakes and it was not clear which of the 3 connectors was the issue.
To replace the whole lead (FB):-
Inside the AS, take out the mattress
Unscrew the bed support panel closest to the front window (about 10 screws).
You will now be able to see down into the front storage compartment, remove the 3 screws that secure the white vertical panel that covers the 7 pin JB and inverter.
This will give you clear access to the 7pin wire connector junction box.
You can probably can get to the JB from the front storage hatch also if you would prefer but you will almost need to crawl in there to see what you are doing.
Open up the 7 pin wire JB (black box towards the front). Your manual will have the pin out diagram for the 7 pin connector with wore colors and locations. Make a note where each color wire goes in the JB and also where it is terminated in the 7 pin adaptor.
I bought this
replacement one off Amazon - may be bit long for you but you can coil up any spare in the storage compartment. Note that the location of the cores by color do not match the one on your AS but there is a sketch with the new cable that will show you what color goes to what pin on the plug so you can match to your AS.
To remove the old cable you will need to CAREFULLY dig out some of the black sealant that seals the hole in the floor of the storage compartment where the cable goes out to the front of the A frame.
You can then start to pull the old cable back.
Make sure you securely tape a pulling wire to the end of the old cable as you pull it back towards the A frame. You will use this to pull the new one back through the A frame and into the storage compartment since the cable is run inside the A frame box section. As you pull back the old wire you will need to drill out a few riveted cable clips to enable withdrawal. I used some cable ties to secure the new cable after refitting in the same general locations.
Pull the old cable back, as soon as you see your pulling wire coming out of the grommet in the A frame, separate it from the old cable, attach your new cable securely with electricians tape and pull back.
Terminate the cable in the JB - check and double check connections.I confirmed end to end correct connection by measuring resistance from the plug pin to terminal in the JB. A few Ohms and you are connected, open circuit and you have something miss wired.
Connect to your TV and check all lights, brakes etc work as intended.
Confirm the free length of cable you want for your TV at the plug end, pull through any excess into the storage compartment and coil up.
Reseal hole in floor with sealant. You can buy the correct Airstream black sealant off their website or get something similar from your automative or home center.
If you have done some wiring previously around the house or in a prior TT or TV you should have no problems doing this yourself.