Why Your Central AC Isn’t Moving Enough Air – Popular Mechanics

My central air- conditioning system doesn't seem to be moving much air. What's the problem?Laura I., Boise, Idaho

Of the things that can contribute to lack of air movement, some are simple enough for you to check. For others, you'll need a contractor.

If the system seems to have slowly and gradually lost air movement, that could be a dirty evaporator coil or air filter. It takes a lot of neglect and a lot of airborne dirt to cause an air-blocking buildup, but it can happen. For example, if your home went through a long phase of remodeling and the contractors didn't do much to keep flying dust under control, that could be the cause. Have a look at the filter, and, if you know where to find it, check the evaporator coil, too. Another source of slow loss of air movement is a fan that's not operating properly. Normally fans and blowers either work or they don't, but one that runs intermittently or is turning slowly (and perhaps even overheating) could cause the problem.

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If the problem occurs suddenly, it could be the ducts. A flex duct (essentially, a large insulated hose) that has detached or been pinched could suddenly prevent air flow. A quick look in the attic is all it takes to spot this. Similarly, if a duct-cleaning company didn't send its A-team, they might have damaged the system or knocked loose a piece of rigid insulation inside a steel duct. This would have the same result.

If the problem appeared soon after having a new system installed, you need to get the contractor back. The problem might be obvious, like a closed damper, or it might take some sophisticated pressure testing to reveal whether there is improper duct sizing or an air filter that's just too restrictive.

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Why Your Central AC Isn't Moving Enough Air - Popular Mechanics