RV Repair: Air lock?, camp trailer, water line

Question
I just bought a used 1997 26' Powler camp trailer. I've never own a camp trailer so this is all new to me. I think I have a air lock in the hot water line. I can get hot water to the kitchen sink and the shower, but I can not get water to the back sink. I'm thinking that
I still have air in the line. Is there any tricks in getting the air lock out.  

Answer
As far as I know, there is no such thing as a air lock happening in an RV water system.  Turn on the faucet and let the air bleed out followed by a stream of water.  You might have a valve in the line somewhere, check if there is one and it's closed.
Check underneath the sink to see if there are any shutoffs.