Came out to call for a system not cooling properly. Customer stated they had a company out a few weeks ago and they added refrigerant to the system. Now the system is doing the same thing. Customer was told something about the coil. Wanted a second opinion on what it was. I checked system over and found it frozen over. Told customer I would have to come back later today, and that they need to leave it off till I come back. I turned the blower fan on to circulate the air for now. Came back out to call to check system. Found the AC low on refrigerant again. Customer wanted me to do a leak search to find a possible leak. Performed leak search and found a pinhole leak in the evaporator coil. Let customer know what I found. Customer wanted me to look up the warranty information tomorrow on the coil and see if it may still be under warranty so they can replace it in the near future. I added 2lbs of 410a to system to get proper charge on system. AC is now cooling properly.