Brought the Sentra to Frigid Zone today. The aircon wasn’t running and I figured there’s a leak somewhere. The diagnosis: there’s indeed a leak and it’s in the evaporator. That’s the bad thing. The worse thing is that I had that same evaporator installed brand new from the same shop just over a year ago. I was naturally rather unhappy but it is past the warranty period (6 months). At least I was able to get a small discount, a longer warranty (1 year), and an assurance, unverifiable until next year, that the new evaporator is of a better make.