I have a 2014 Silverado LT. Started seeing water puddling in the floor mat on the driver side near the parking brake. Took it to the dealer and it turns out....surprise, surprise.....the high frequency antenna on the roof is leaking. It is sounding like this is a well known problem to GM, but for whatever reason they will not acknowledge that is a persistent problem.
My AC started blowing warm air about a week ago, so I had them check that too. Turns out there was absolutely NO freon left in the system. After recharging and pressure testing, they found NO leaks. I am no physicist, but it is my understanding if there is a substance in a sealed system and it disappears then it must have leaked out.
I have a sick feeling this won't be my last visit to the shop with AC issues.