Hmmm. The symptoms don't exactly match, but I suggest unplugging the auxilliary electric water pump to see if there is any change in operation. The electric pump is activated to feed hot coolant to the heater anytime the climate control decides to warm things up a bit. On a mildly warm day it will mix in a little heat to prevent the a/c from overcooling the cabin.

The electric pumps eventually seize up/short out. This puts the climate system in a sort of protection mode to avoid damage to the electronics. The symptoms are no a/c, no fan, hot air out the defrost and side dash vents.

Unfortunately I don't know exactly where the pump is located on your particular car. Hopefully someone will chime in with that information.

- JimY