Yes it is the blend door motor. The rhythmic clicking sound you hear is the blend door trying to move. It will not move because the actuator for the blend door has teeth broken from the driven gear inside the actuator.
Seen this happen a lot, including my wife's van. The actuator is usually white and is located above and behind the ashtray. Actually it's attached to the plenum chamber in that location.
Remove the cover between the ashtray and the floor, (four screws), stand on your head under the dash and put your hand on the part I just described and you can feel it when it "clicks". Disconnect the electrical plug and the clicking will stop. About 30-40 bucks at ebay motors.
Sunday, January 25th, 2009 AT 3:32 PM