Ah, the sweet relief of a cool, dry house after a hot, sweaty afternoon of yard work. Like any mechanical system, air conditioning needs a little TLC to run smoothly, including many tasks you can tackle on your own. Sometimes things can happen that would cause you to need air conditioning repair services. These tips below can assist in preventing these issues. We asked This Old House plumbing and heating expert Richard Trethewey to share his know-how for central air conditioning repair and window units.

Change Filters

Dirty filters kill your air conditioning efficiency, so install a new one every month during the cooling season for central and window units (or clean them if you’ve got the washable type). Look for the filter’s minimum efficiency reporting value, or MERV, which ranges from 1 to 12 for home air conditioning units; the higher the number, the better filtration it provides (and the more energy needed to pull air through it, so balance air-quality concerns with energy costs).

Fix Leaks

Ducts can lose up to 30 percent of airflow through leaks, and window air conditioning units are notoriously tough to seal properly. Find leaks using the old “smoke trick”: For window units, light a stick of incense and hold it where the unit and the window frame meet; for central air conditioning, hold the stick near duct connections. If the smoke blows around, you’ve got leakage. For ductwork, use foil tape to seal small gaps and duct mastic for larger ones; for window air conditioning units, stuff foam between the device and the window frame, taping as needed.

Use a Timer

There’s no need to blast the air conditioning at full tilt while you’re at work. For central units, install a programmable thermostat that lets you set higher temps when you’re gone and cooler temps when you’re home. Newer window units have built-in timers and adjustable thermostats, or you can buy a timer at any home store for $10 to $20; just make sure it matches your device’s voltage. Unless you’re going on vacation, don’t shut off the system; otherwise, the air compressor will need to work harder to cool your house later.


Ducts in hot attics or crawl spaces should be wrapped to keep the air within them cool. You can use spray foam, batt insulation, or rigid-foam insulation. Seal batt and rigid insulation with foil tape (not duct tape). For tight spaces, wraps like Reflectix offer some degree of insulation.

Service Compressor/Condenser

A central air conditioning system’s air compressor and condenser are usually located outside the house, close to your foundation. It works best when there’s about 24 inches of clear space in all directions, so get rid of nearby shrubs, tall grass, leaves, and hanging branches.
TOH Tip – “Install condensers or window units on the north or east side of your house, or build a screen to shield them from the sun. Putting them in direct sunlight reduces their efficiency by as much as 10 percent.”

Keep Unit Cool

Extend the life of your air conditioning system by keeping blinds or shades down during the day; you can also install awnings to shield south-facing windows from intense sun. Consider running the air conditioning in conjunction with floor or ceiling fans to circulate cooled air more effectively.

Maintain Unit

The dealer who installed your central air conditioning (or one you find locally) should put you on a yearly cleaning schedule that goes beyond just cleaning the filters. Schedule this air conditioning repair maintenance check up before the cooling season starts (or do it now if you didn’t do it earlier this year), and make sure it includes the following tasks: cleaning and inspecting coils; cleaning or replacing filters; adjusting and replacing fan belts; lubricating motors and bearings; cleaning and checking blowers and fans; inspecting controls and safeties; checking refrigerant and pressures; and verifying operating temperatures.

Get Airflow

Shutting too many interior doors causes central air conditioning systems to go out of balance, meaning there’s less airflow in the entire house. If you want some privacy, keep doors slightly ajar instead.


Federal laws require AC units to be a lot more efficient than they were just 10 years ago. For central air conditioning, look for the seasonal energy-efficiency ratio, or SEER; for window units, the measure is simply called the energy-efficiency ratio, or EER. The standards mandate a SEER of 13 and an EER of 8, but devices with higher numbers will cost less to operate. – This Old House

AIRMAX Heating & Air operates 24 hours a day, always ready to assist you with any heating and cooling needs you may have. We are a family owned Air Conditioning & Heating business and offer air conditioning repair in Charleston, Berkeley, Dorchester as South Carolina’s Top Choice!

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