The Care & Feeding of Your Home: DIY Air Conditioner Maintenance

By Handyman Bob Strong07 Ice Cube Head

Temperatures may soon be heading north of TOO HOT! We’ll all be running our air conditioners 24/7 in an attempt to stay cool and that means we better check to make sure they can handle the load. So, what can we do as homeowners and Do-It-Yourselfers? Make sure the furnace filter is clean, make sure the outside fan unit is free from shrubs and weeds, and make sure the condensate is actually draining to the outside. That’s about all we can do for ourselves.

Let’s quickly review how an air conditioner works, so you’ll understand why those three things are so important. The A/C system is a closed loop, made up of tubing that circulates refrigerant, along with a compressor and a couple of fans.

Outside your house is a metal housing with a fan, a compressor and a coil of tubing with refrigerant in it. The tubing is a continuous loop that comes from and returns to another coil attached to the furnace inside your house or maybe it’s in the attic or basement or garage. The whole system is really a heat exchanger. By manipulating the pressure of the refrigerant in the tubing, the manufacturer causes the coils in the furnace unit to be very cold, somewhere in the 30 degree range.

So, here’s what happens when you turn the A/C on and set your thermostat below the existing room temperature. The outside fan comes on, the compressor begins to operate, and the furnace blower comes on, circulating air in your home. As this circulating air passes across the cooling coils, heat energy is exchanged, leaving cooler air to return to the house. The refrigerant, now warmed by the heat exchange, continues to the outside coils where the outside fan helps to cool it down and the process continues until the air in the house reaches the desired temperature and the system shuts off. A typical system is designed to reduce the ambient temperature by about 20 degrees, so on a 95 degree day, your system should be able to keep your home at about 75 degrees.

Air conditioners perform another function that increases our comfort; they remove most of the humidity from the air. Think about what happens on the outside of a glass of iced tea in the summer; moisture forms and drips onto the table. That’s water vapor in the air condensing into a liquid and that’s exactly what happens in an air conditioner. The moist air, leaving your home and passing across the chilled coils in the furnace, condenses and drips into a drip pan. The collected water then drains through a pipe to the outside or, if your furnace is below ground level, it flows into a floor drain or condensate pump that pumps it to the outside.

Now, let’s tie it all together. If the furnace filter is dirty, air flow is restricted, so you won’t get all the cool air into the house that you expect. Also, restricted air can result in the cooling coils freezing up, which is really hard on the equipment.

If shrubs and weeds are allowed to block the outside fan unit, it can’t draw in enough air to properly exchange the heat from the system.

And, finally, if the condensate isn’t finding its way to the outside, that means it’s staying somewhere in your home – in the attic, in the basement, in the crawl space, or in the garage – and you don’t want water in any of those places.

So, be sure to add these three things to your honey-do list:

  • Check the furnace filter and change it if necessary.
  • Check to make sure the outside unit is free of weeds and shrubs.
  • Check to make sure the condensate is draining outside your home.

Handyman Bob offers home improvement advice on his radio show, Around The House, every Saturday from noon to 2pm on FM News 101 KXL. And, during the week, he provides residential and commercial asbestos testing services for homeowners and contractors. Visit for details.