An internal VAV damper blade drops shut and blocks airflow
If the actuator moves but the internal damper blade drops or disconnects, the issue may be mechanical linkage/shaft failure inside the box. Verify access, blade movement, and linkage before blaming controls.
Do not replace controls parts before proving the internal damper blade is still connected mechanically.
Check
Confirm actuator command vs actual blade movement.
Check for no-air complaints, zero CFM, and mechanical noise.
Use approved access method to inspect damper shaft/linkage.
Verify blades move freely and are not binding against casing.
Repair linkage/shaft connection and retest controls/TAB.
Steps
Confirm actuator command vs actual blade movement.
Check for no-air complaints, zero CFM, and mechanical noise.
Use approved access method to inspect damper shaft/linkage.
Verify blades move freely and are not binding against casing.
Repair linkage/shaft connection and retest controls/TAB.
Say this to your foreman
VAV [tag] has actuator movement but the internal blades appear dropped/blocked. I checked airflow and linkage access. Do you want me to open access and reset the shaft/collar connection?