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Apprentice answer

Why would a VAV show zero airflow even though the actuator is running

3rd YearAirflow, TAB, Startup & TestingCheck first

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.

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Plain-English answer

A VAV can lose airflow when the internal damper shaft, collar, pin, or linkage slips and the blades fall shut. The actuator may still make noise or move without moving the blades.

Use existing access if possible. If access is needed, get direction before cutting. Verify blade movement by hand when safe, inspect shaft/collar linkage, reset or repair the mechanical connection, then patch/seal and have controls/TAB retest.

Ask 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?

Verify before acting

Use this as training guidance. Foreman direction, approved drawings, project specs, manufacturer instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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