No airflow from dash defrost vents.

Cole Shannon · November 14, 2023

I've got a 2018 1500 5.3L silverado. My H/VAC systems all work great, with one exception. When I select defrost mode, I notice I still hear the fan blowing, yet no airflow coming from my defrost vents. When this is happening, no air is coming from any other vents either (which is to be expected). What do I check? Is there any useful guides or viedeos out there to help? thanks in advance.

mikeyk101 · November 15, 2023

Maybe it needs a recalibration of the HVAC system? Take a look at this post for some info but there are other threads on this as well.

Cole Shannon · November 15, 2023

11 hours ago, mikeyk101 said:

Maybe it needs a recalibration of the HVAC system? Take a look at this post for some info but there are other threads on this as well.

I will give this a try and report back. Many thanks

Cole Shannon · August 28, 2024

Reviving this thread as colder weather is apporaching again... I tried re-calibrating the system using the method above but no luck. Still no airflow when I go to defrost mode. Would this be a problem with the blend door actuator?

mikeyk101 · August 29, 2024

Unfortunately it might be. There are folks here much more knowledgeable on these kind of things so hopefully they will respond shortly.

Cole Shannon · September 3, 2024

After doing some more research I think my probelm is with this part: https://www.amazon.com/ACDelco-15-74349-Original-Equipment-Conditioning/dp/B00S0JJM8O

The mode actuator, not the blend actuator. If figure its the mode actuator because all my temp controls work fine, it's just going to defrost mode that prduces no airflow out of any vents besides the footbox. Looks like it could be a major pita to get to. I will start with replacing this and report back if my problem is fixed.