i Have a 2004 chevy silverado. i started hearing this tapping behind the dashboard now i have no cold air blowing out of vents. the temp control doesnothing.it almost sounded like relay clicking. anyone have a clue what it could be before i take dash apart?

 

it blows..but hot?...are you SURE its hot out both sides?..not just the drivers' side?

 

positive. hot air only both sides. it almost sounded like there was flap in the duct work that broke. i am not sure if i thinking right or not. was hopeing someone knew before i ripped dash apart.

 

the temp actuators love to go out...but there is a left and a right..I doubt both conked.
Its almost always an actuator...but just 1 side.

It really needs to be scanned for codes.

And I have no clue of your technical knowledge/tools...but that ain't no easy task...removing the dash on that.