i have a 2001 explorer sport and when i turn the climate control knob from a/c to heat i have not change (steady cold a/c). i do hear a clicking coming from the compressor under the hood every 15 or so seconds in the hot or cold position. i have replaced my thermostat and checked heater hoses to verify circulation. i have read many post talking about blend door and the motor so i tried the quick fix where you cut into plenum and manually move the blend door. when looking into the cutout i noticed that the door was opening and closing when i changed the climate control from hot to cold and still no heat. i moved the blend door by hand and no change just cold air. i disconnected my heater hoses and blew into the intake line and fluid came out of return line (not sure if that means anything). any help would be appreciated.