I drive a 97 Cherokee sport, and just recently the air has completely stopped coming out of all the vents except for the defrost. When the air control dial is on (even on a low setting) and I crack my window, the defrost vents make a loud whistling sound.. any suggestions on what to check? It hasn't been stalling and I don't have cruise control. Also my temperature gauge is always on 150, like right when I start it, before it has a chance to warm up.. it used to run about 200..

Any help would be greatly appreciated!
Emily