The AC is running, and you can feel a steady stream of cool air from the hallway and bedroom vents. At the office vent, there’s barely a breeze. Weak airflow from one vent often starts with a local issue. The supply register may be partly closed or covered, or the duct branch feeding that opening may be restricted, leaking, or disconnected.

Check the register first. Make sure its louvers are open and that a rug, piece of furniture, or curtain isn’t in the way. Then compare it with a similar supply vent while the AC is still in the same cooling cycle. If nearby vents blow normally and that one stays weak, an HVAC technician can trace the problem from the opening back through its duct branch.

Start at the supply register

A supply register delivers cooled or heated air into a room. A return grille draws room air back toward the HVAC equipment. During a normal cooling cycle, hold your hand a few inches from the opening. At a supply register, air blows toward you. At a return grille, air moves toward the opening. Compare supply registers so you’re checking openings that perform the same job.

If the register has an accessible lever, check that the louvers open when you move it. A lever can move even if a louver sticks. Look for anything that blocks the opening or hangs in front of it. A rug that covers half a floor register or a curtain hanging across a wall register can make it hard to feel the air reaching the room. Clear the space if you can do so safely, then check the airflow again.

Choose a nearby supply register of roughly the same size and style for comparison. Feel for airflow during the same cooling cycle, with both registers in their usual open positions. This is a rough check. Register shape and louver angle affect how the air feels against your hand, and different rooms can be designed to receive different amounts of air. A noticeable drop from what that vent used to deliver is especially worth mentioning.

Trace weak airflow from one vent back to its duct branch

A duct branch is the section that carries air from a larger supply duct to a register or group of registers. Once the grille is open and clear, a technician can check the parts of that path that are safely accessible.

• Partly closed balancing damper. Some branches have an adjustable plate inside the duct that controls how much air enters the branch. Its position can limit airflow even when the room register is fully open. A technician can check its setting and measure airflow before making an adjustment.
• Crushed or kinked flexible duct. Flexible duct can narrow where it is squeezed or bent sharply. If the weak airflow began after attic work or after items were moved near the duct, mention that timing when you call.
• Loose or disconnected connection. Air can escape through a gap where the branch joins a larger duct or connects to the fitting behind the register. The vent may still deliver some air, depending on the size and location of the gap.
• Obstruction in the branch. Debris or another physical blockage can restrict airflow. Ask the technician to identify where the obstruction is and what it consists of so you can choose the appropriate fix.

Note whether the change happened suddenly, followed recent work, or has been there since you moved in. A sudden drop gives the technician a reason to look for a recent change. A vent that has always been weak may call for checking the original damper setting or how much air the branch was designed to carry.

Check whether one vent, one area, or the whole house is affected

What an HVAC technician can measure

If the vent stays weak after you clear it, ask an HVAC technician to measure airflow at the register and compare it with the amount the room is intended to receive, if that information is available. A measured reading is more useful than how the air feels against your hand. The technician can then inspect the register connection, branch duct, and any balancing damper. If several readings are low, they can look farther upstream for a shared restriction.

If you discuss a suspected duct problem with Green Wood Air Duct Cleaning, share which vent is affected, when the change started, and any airflow readings or photos from the inspection. Ask whether the finding calls for a duct repair or whether the technician identified debris that cleaning could remove.

When cleaning or repair makes sense

A crushed duct needs its shape and airflow restored. A loose connection needs to be secured and sealed, and a damper setting may need adjustment based on measured airflow. If the inspection finds substantial buildup or removable debris obstructing the branch, ask whether duct cleaning would clear it and how airflow can be checked afterward.

If an inspection identifies a damaged duct branch or a debris obstruction that cleaning can address, Austin-area homeowners can contact Green Wood Air Duct Cleaning about residential duct repair or cleaning. Share the affected vent and what the technician found so the proposed work addresses that specific branch.