Turned on heater to blow on floor and heard a pop. Now air blows from floor only on 1999 GMC Sierra 1500

Air stuck blowing from floor and defrost only

by in Richardson, TX on April 01, 2013
1 answer 2 comments
ANSWER by , April 01, 2013
COMMENT by , April 01, 2013
thanks for the direction to start . could you tell me where blend door is located. Have not been under a dash in 20 yrs. Im a fork lift mechanic now.
COMMENT by , April 02, 2013
there are 3 blend doors rt, left and middle. 1 is by gas pedal one is center of dash amd pne is under glove box area.