Air conditioning is tricky, so many people (even professionals don't do air conditioning repairs properly and end up doing more damage than good). The system needs to be checked for leaks, evacuated, leaks repaired retested for leaks, then recharged. Pressure gauges to measure low and high side pressures are needed as well. Kia as a car manufacturer put a lot of great technical information and work shop manuals on line for free for Kia owners. www.kiatechinfo.com
I have the same issue. Finally took it to a repair place, they told me I had a small leak somewhere because it would not hold the vacuum and I only had 5 ounces of Freon still in. Upon further checking after filling with Fr, the compressor would not turn on at all, which I knew. Their calls for compressor $1200 and $1700. Crazy, but told there was an unusually high demand for them right now and I should ck my warranty or recall. Warranty 60K, I now have 82K, no recalls. BUT KIA said they would replace for $700 plus tax, including labor! HUH?