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Troubleshooting and Repairing Your Central A/C

What should you do if your central air conditioner is not working properly? You can fix some problems yourself. Others will need the attention of a heating and cooling contractor.

First Steps

If your central air conditioner will not run at all, here are three troubleshooting steps you should take before doing anything else:

  1. Check that the electrical disconnect switch, which is usually located in a metal box mounted to the outside of the house near the outside unit, is not off. If it is, turn it on.
  2. Check for a tripped fuse or tripped breaker in your main electrical panel.
  3. Make sure the thermostat is set to “Cool” and that the temperature setting is not too high. This is something that people often overlook when going from winter to summer. Also check the thermostat batteries and change them if needed.

These are simple steps, but they can save you an embarrassing and potentially expensive service call. Here are a few other common central air conditioner problems:

A Noisy Unit

Like most equipment with several moving parts, AC units can make several noises, some louder than others. For instance, a grinding noise can mean a problem with a fan motor. A rattling noise could be caused by something minor like loose cabinet screws, but it can also be a sign of a worn compressor. And a slight hissing noise could be a sign of a refrigerant leak.

Frost build-up

Improper airflow due to a dirty filter can cause the air conditioning unit to freeze. Dirty filters can cause a variety of problems, so it is important to clean or replace your filter regularly.

A damaged blower fan can also cause the coils to frost up, as can a faulty control relay.

Refrigerant Leak

If your central air conditioner is low on refrigerant, chances are good that it has developed a leak. If it is leaking, simply adding refrigerant will not solve the problem. You will need a trained technician to repair the leak and refill the refrigerant. To perform efficiently, a refrigerant charge should conform to the manufacturer's specifications.

Your AC is Blowing Warm Air

This is another problem that can be caused by dirty filters. If your central air conditioner is not producing enough cold air, the first thing to do is check the filter and clean or change it, if needed. Another possibility is that your unit is low on coolant. If so, you’ll need to contact a licensed repair technician to check for leaks and recharge the system.

The Unit Runs Continuously

There are a few possible reasons for this problem. A unit that runs for a very long time may be too small for your house or may not have been installed correctly. Another possibility is that the thermostat is on the wrong setting or needs new batteries. A bad relay switch or a unit that is low on refrigerant can also prevent it from shutting off. And yes, a dirty filter can contribute to this problem, as well.

Usually, keeping the A/C components clean can help to prevent many problems. Dirt may make the compressor or fans fail before they should. Regularly clean or replace dirty filters to keep your unit functioning properly. Always keep the manufacturer's manual handy and if you don't have one, request one from the manufacturer.

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