Hi, I noticed that our AC unit was not cooling well and determined that the copper liquid line going into the air handler, which is in a closet in the upstairs hallway, is very cold when the AC is running. I removed the front panel of the unit, and the smaller liquid lines feeding the coil get frosty when the unit is running. The bottom few inches of the coil also becomes cold, but the top 75% of the A frame coil is not cold at all. On the outside unit, the air leaving the top of the unit is also ambient temperature, it is not warm like it is normally. Replaced the capacitor on the outside unit just in case, but that did not help. Any suggestions on what could be the possible issue would be greatly appreciated. (The unit is a 3.5 ton and 12 years old.) Thanks in advance for any suggestions.