I have been having a problem with my defrost/vent control. I have a 04 silverado with the upgraded hvac controls.

I can not get it to switch off of defrost. I push the button to switch from defrost to vent. The symbol for vent shows but it is still blowing out the defrost.

If I change it to the symbol for the floor it still blows out of the defrost.

Has anyone seen this problem before? This all started after I replaced my battery.

Souds like you may have moved/removed a vacuum line somehow. I believe these are vaccum operated controls. Anyone else know for sure?