If after 4 weeks, the chrysalis looks healthy, then it probably IS the temperature. Though it is still possible that something is wrong with it. For weddings and other events, they put the chrysalis in refrigerator to delay eclosure for several days to a week. 4 weeks seem rather long, but AC vents are supposed to blow out air that's 10Â°F colder than the thermostat setting. So.... And as you said, their wild fellow butterflies are emerging in the 90Â° outside temperature.
I would definitely move it away from the AC vent and put it where morning to mid-morning sun can reach the chrysalis. Blocking the vent was a good idea.
I replied to your other thread
. I'm going to lock this one so you won't be getting butterfly and caterpillar related comments on both threads. But go ahead and create new topics if you have specific questions.