My AC wasn't working so I called a tech. They came out and determined that my refrigerant levels were low and added refrigerant as they explained 4 lbs worth. They said I may have a leak and added dye on the outside unit to potentially discover the leak. $800 later my AC was working perfectly fine and everyone was happy.
Fast forward five days, my pipe on the inside is completely frozen and my AC is not working. It's running on the outside but not on the inside. I shut the system down and laid towels around the inside unit while it defrosts.
Question: What can be the problem, considering the tech was just here five days ago and gave me more refrigerant?
I'm down a good chunk of money and just trying to better understand what is causing this issue. I'd like to better educate myself and know that what I'm being told about the problem is the actual problem without any hidden meaning and agenda.