let's make sure we are on the same page.When you say "condenser" are you referring to the coils that are exposed when you remove the filter?? or the coils that you see when you look at the a/c from outside the house? If you are talking about the coils behind the filter (evaporator coil) then cleaning them is much easier than cleaning the outside condenser coils. In either case use a stiff tooth brush and clean the dirt of the coil fins. VERY IMPORTANT.....move the brush only parallel to the fins on the coil and be gentle. If you wipe the brush ACROSS the fins you will bend them which will severely restrict the airflow. If after that the unit is still not as cold as it used to be , feel the evaporator coil with your hand. It should feel cool from top to bottom(while a/c is in cooling mode).If it is only partially cool then the sealed system has lost some of it's refrigerant charge. If that's the case I would not recharge it. Chances are you will have to charge it every year. Not worth it on a 10kbtu unit
A little advice from an "Ole Timer". Dow foaming bathroom cleaner and a spray bottle filled with plain water. Spray the foaming cleaner on the coils (evaporator & condenser). You will see the dirt foam out then rinse with the clean water. JMO
Shined a flashlight into back of ac when I was outside. The front of the condenser had some dirt on it in places. Thought that might affect cooling. Thought of spraying water on it to clean it. Some fins bent but not that many.