I have a 2002 chevy venture. the heat has stopped working. when i used to turn the heat/cool knob to heat it would make a popping sound and the heat would kick in. now when i turn the same knob there is no sound or heat. i was told it may be some blendor switch or valve but im not sure what or where that is. please help if you can. its cold

Cars & Trucks - Chevrolet - Venture - 1997 Chevrolet Venture