2005 Sierra 2500hd Heater Problems

[MarvinM]

Hello All,

Just recently purchase a used 2005 Sierra 2500HD C.C, Duramax with dual climate controls.

The problem I'm having is in the performance of the heater... all controls seem to be functioning properly (changes are noticed when controls are changed from floor to vent to defrost) but there just seems to be low air flow in all selections. Due to a bearing noise, I recently changed the fan blower motor so that is not the issue. In fact the blower motor seems to be moving plenty of air when not installed in the plenum. I read on some sites about doing a calibration of the blend doors and that didnt seem to have the same symptoms nor did several calibration attempts change the performance.

The temp is the same on both sides and the controls change where the air goes, there just isnt much air flow.

 

Any help with this issue would be greatly appreciated.