When an air conditioner is working perfectly, you should get abundant and even airflow from each duct in your home. What, then, does it mean when one or more of your ducts have low airflow but others are still working? Your air conditioner is obviously not completely broken, but there is a problem at hand. Here's a look at some likely culprits.
1. Blockages in the ducts.
It's possible that there is something inside the ducts leading to the low-flow vents that is stopping the air from reaching them. Mold and dust are unlikely to have this profound of an effect, although they can build up in ducts over time. However, it's possible that a bird built a nest in the duct or that a child shoved a toy down the vent. Remove the vent cover, and see if you can see anything. If you can't, this is something to have your HVAC contractor check more thoroughly when they arrive to take care of your home.
2. A failing fan.
Your air conditioner has a powerful fan attached to it. That fan propels the cooled air through your ducts. If the air is no longer reaching the ducts that are furthest from the fan, that could be because the fan is not generating enough power anymore. Listen closely when your air conditioner is running. Do you hear any squeaking, grinding, or rattling? This may indicate that the fan has a failing ball bearing or belt. These are easy things for your HVAC contractor to fix, and you should have them fixed soon before the fan fails completely and none of your vents get air!
3. Leaky ducts.
Another possibility is that one of your ducts has detached itself from the system, causing some or all of the air passing through it to leak out between the walls. To tell whether this is a likely explanation for your woes, wait until the AC has run for a while, and then run your hands over the walls near the vents that are not getting much air. Do the walls have any cool spots, or do you notice any spots that feel damp? This could indicate that the air is leaking out of the ducts rather than making it to the vents. Your HVAC contractor can re-attach the vents and seal the leaks so this does not happen to you again.
4. Undersized air conditioner.
If you recently moved into the home and do not know its history, there is a possibility that the air conditioner is undersized and never delivered adequate air through the system in the first place. Sizing an air conditioner can get complicated since it depends on the layout of the home, number of rooms, and so forth. A good guideline to consider, however, is that you need about 1 ton of AC for every 400 square feet of home space. So if you have a 1600-square-foot home and your AC unit is not at least 4 feet, it is probably undersized. Upgrading to a larger unit will not just allow for more even cooling, but will also save you money on air conditioning bills since the new unit won't have to run as often.
If you are not getting adequate airflow at all of your vents, do not ignore this issue. You deserve to have a comfortable home that is evenly cooled, and an air conditioning repair company like Bronco Plumbing Heating & Air can help you achieve that. Talk to them about your problems. They can come take a look and either fix your vents, fix your fan, or recommend an AC upgrade with will work for you.