Central Air Conditioner Repair

What can you do when your central air conditioner doesn’t cool your home effectively? This Fix-It Guide for central air conditioner repair tells how a central air conditioner works, what often goes wrong with a central air conditioner, how to identify the problem, and what parts and tools you will need to fix a central air conditioner. It then gives simple step-by-step instructions for how to replace a filter, how to clear the central air conditioner evaporator drain, and how to tighten loose fan blades. You may be referred to other Fix-It Guides for appliance control repair and forced-air distribution repair.

How Does a Central Air Conditioner Work?

Central Air Conditioner RepairA central air conditioner is a large appliance system that cools an entire residence. It has two separate components: the condenser and the evaporator. The condenser unit typically is located outside the house. The evaporator coil is mounted with or near the heating furnace, so the furnace blower can circulate the cool air throughout the house. Coolant lines run from the condenser to the evaporator, taking heat from the house and moving it outside.

What Can Go Wrong with a Central Air Conditioner?

Air conditioners are complex and repairing them requires specialized training. Even so, you can handle routine maintenance and some minor repairs yourself. If not, you can more clearly explain to the technician what’s wrong, saving the technician some expensive time on your air conditioner repair.

Fix-It Tip

You can reduce repair costs by having your central air conditioning system checked and tuned up once a year–maybe during the fall when air conditioning technicians aren’t as busy. They will test the refrigerant and other components as well as clean the unit. You can save a few bucks by cleaning it up and replacing filters yourself before the technician arrives.

How Can I Identify the Central Air Conditioner Problem?

  • If the system does not run, check the electrical service panel for a tripped breaker or blown fuse. Also make sure the thermostat is set correctly.
  • If the system runs but does not cool, check for a clogged filter or malfunctioning blower. Inspect the condensing unit for blockages. If it still doesn’t cool, call a technician to recharge the refrigerant. Note that some systems include a location for visually inspecting for low refrigerant.
  • If the system cycles too often, check the condensing unit’s airflow, then the filter and blower; check the thermostat (see the Appliance Controls Fix-It Guide).
  • If the outdoor unit is noisy, check the fan for obstruction. Tighten loose fan blades (see below) or loose screws in the housing.
  • If water drips from the bottom of the evaporator when the air conditioner is running, clear the evaporator drain (see below).
  • If some rooms are too cool and others too warm, the distribution system may require balancing; see the Forced-Air Distribution Fix-It Guide .

Fix-It Tip

Once a year, lubricate the fan motor with lightweight non-detergent oil if the owner’s manual has instructions for doing so. If you don’t have the manual, ask the technician how you can do this task yourself.

What Do I Need for Central Air Conditioner Repair?

There are very few parts you will be able to replace on a central air conditioner, except for filters. You can purchase filters at larger hardware stores and home centers or through the manufacturer or aftermarket supplier. The tools you may need for basic service include:

  • Screwdrivers
  • Wrenches
  • Garden hose

What Are the Steps to Central Air Conditioner Repair?

Replace a central air conditioner filter:

  1. Locate the filter(s) in the unit. Some are located on the condenser while others at the evaporator.
  2. Remove the housing as needed to access and remove the filter.
  3. Take the filter to a hardware store or home center for an exact replacement. If you need it, a part number may be on the filter or in the owner’s manual. If a part number is not available, write the central air conditioner’s model number down and take it with you for cross-referencing.
  4. Reinstall the filter, making sure that the area around the filter also is clean of debris.

Clear a central air conditioner evaporator drain:

  1. Remove the trap from the elbow.
  2. Flush the trap with a garden hose, then pour in 1 tbsp. chlorine bleach through the trap to clean it.
  3. Reattach the trap to the elbow.

Tighten loose central air conditioner fan blades:

  1. Visually inspect the setscrews on the fan’s hub for obvious damage or a loose screw.
  2. If they are loose, tighten the setscrews with a wrench or screwdriver.
  3. Check the fan’s rotation to make sure it is smooth.

Fix-It Tip

Before restarting your central air conditioner in the spring (or after any long shutdown), turn power on to the unit for 24 hours before actually using it. This produces the heat needed to separate the oil from the refrigerant in the compressor.