Weak Airflow
When the AC is clearly running but almost no air comes from the vents, the most likely cause is a severe restriction at or before the blower — commonly a frozen evaporator coil, an extremely clogged filter, or a failed blower motor. This pattern is rarely a duct problem, since duct leakage reduces delivered airflow but does not typically cut it to nearly nothing.
When the coil ices over, it physically blocks the passage of air through the equipment. Airflow can drop to almost nothing even though the blower is running, because the ice itself is the obstruction rather than anything downstream.
A filter that has gone unchanged for a long time can become nearly solid with debris, choking off airflow at the point of entry before it ever reaches the coil or ductwork.
A motor that is running but has lost most of its capacity — due to a failing capacitor, worn bearings, or an electrical fault — can turn while moving very little air, sounding largely normal while producing almost no output.
A section of flex duct that has fully collapsed, rather than merely kinked, can act as a near-total blockage at that point in the system, sharply reducing airflow to everything downstream of it.
Low refrigerant charge or a metering fault can cause the coil to run too cold and ice over, which is a mechanical and refrigerant issue rather than anything to do with the duct system.
Stick to what you can see, feel and hear. Leave electrical panels, refrigerant, combustion appliances and equipment internals to a licensed professional.
Duct leakage reduces the volume of conditioned air that reaches the rooms, but it does so by letting air escape along the way — it does not typically prevent the blower from moving air in the first place. A near-total loss of airflow at the vents, with the equipment still audibly running, points to a blockage at or inside the equipment rather than air escaping downstream in the ducts.
Once an equipment-side cause has been ruled out and normal airflow is restored, if delivered airflow at the registers still seems low relative to what the equipment is producing, a duct leakage test can determine whether leakage is separately reducing what reaches the rooms.
Duct Daddy specialises in duct leakage testing and duct sealing. We do not perform mechanical HVAC repair, refrigerant work or equipment replacement. Contact a qualified HVAC contractor if any of the following apply:
High indoor humidity in Southeast Louisiana homes can accelerate coil icing when airflow is already restricted, making a near-total airflow loss develop faster than it might in a drier climate.
See the communities we serve.
Every register in the house blowing softer than it should, and what that pattern usually points to.
A fresh filter didn't fix it — what to check once the most obvious cause has already been ruled out.
Continuous runtime without a satisfied thermostat means capacity or delivery is falling short of the heat load.
A system that never shuts off is either matched to a heavy load and doing its job, or is losing capacity or air faster than it can produce it.
Cooling and dehumidifying are not the same job, and a system can do one without the other.
Weak airflow across the whole house, doors that resist closing, and a struggling system can all point to a starved return side.
Browse every symptom in the troubleshooting center.
Schedule a duct leakage evaluation and get measured numbers for your home — not a guess.
