Your outdoor unit's job is to get rid of heat
Your air conditioner pulls heat out of your house and dumps it outside through the coil in the outdoor unit. Air has to pass freely through that coil for it to work. When the coil gets covered in lint, dirt, leaves or cottonwood fluff, the heat has nowhere to go.
The photos below are from one of our recent maintenance visits. The coil on this Lennox unit was so caked over you could barely see the fins.
What a dirty coil does to your system
- The system runs longer to cool the house, so your electric bill goes up
- Pressures and temperatures inside the system climb, which strains the compressor, the most expensive part to replace
- It's more likely to fail on the hottest days, exactly when you need it most
- The house may never quite reach the temperature you set
Clogged filters cause problems inside
The air filter protects the indoor side of your system. When it fills up with dust, air can't get through. That can make the system run longer, leave rooms stuffy, and in some cases cause the indoor coil to freeze up and stop cooling altogether.
What you can do between tune-ups
- Check your air filter every month and replace it when it looks gray. Many homes need a new one every 1–3 months, sooner with pets or during wildfire smoke
- Keep plants, weeds and stored items at least two feet away from the outdoor unit
- Gently rinse loose dust off the outside of the unit with a garden hose, with the power off. Never use a pressure washer, which can bend the fins
- Write the filter size down (it's printed on the frame, like 20x25x1) so you always buy the right one
What we do on a maintenance visit
On a tune-up we take the grilles off, clean the outdoor coil properly, check the filter, clean the drain line, test the electrical parts and safety controls, and tell you plainly what condition your system is in. Once a year is usually enough to keep things running well.