I have a 2005 Kia Sedona, and recently had been using a chain garage to fix this and that on my vehicle. I had some pulley noise a few months ago, and they checked it and adjusted it. Last moth the noise was back, and when they recommended I replace the idler pulley. Immediately after I picked up the car, the a/c was not blowing cold (I live in Florida, so of course I noticed this right away.) I brought it back in, they checked it, and said I probably had a slow leak, and they would charge it with freon and that I was to come back in a few days to check it with a black light. Also, I should run the a/c a lot. Well, it ran cold for a few hours, and was out of freon in less than 24. They put the car up, showed me with a black light a few glowing drops, and said that I needed an $1100 new compressor. I asked him to show me where the pulley was they replaced, and it was right next to the compressor. I had zero problems with it until they made the pulley replacement, and they are trying to get me to believe that it was a slow leak. Like I said, I live in Florida, and use it year round. Besides, if it was a slow leak, why was all the freon gone in a few hours? They are telling me there is no way they could have damaged it, but are now offering to do the work for 50% off.
Those glowing drops should have a trail that leads to the actual point of leakage. If there is no physical damage at this point, then it is not their fault, just bad timing.
If the point of leakage is either one of the ports to the system, then all you need is new schrader valves. They only cost a few dollars plus a refill. If they had to move the compressor to replace the idler pulley, they might have caused a leak at one of the hoses and all you need is one or two new o-rings, again only a couple of dollars plus a refill. Not their fault either, it just happens, nature of the business.
Since they were testing for a leak, they may not have filled your system, just put in a little freon with a leak detector so it could still be a slow leak, but they are not allowed to fill the system until the leak is fixed or they lose their license with the EPA for AC work.
I am a little concerned about their competency since they jumped on the new compressor so quickly without apparently checking those other things first.
I cannot see your compressor so I don’t have a clue as to what is leaking or why it began leaking but it would be advisable to get to another shop immediately to have the leak investigated. Over the years I have seen several automobile problems that were almost certainly the result of sabotage done by a mechanic to make a highly profitable repair necessary on the vehicle of a customer who appeared to be financially able to handle the bill while too unfamiliar with the automobile to recognize the flim-flam. Those mechanics make life miserable for all the honest people in the business.