California is roasting in the middle of a historic heatwave. Electric utility providers across the state have instituted rolling blackouts. Death Valley shattered a high temperature record that stood for over a century. We’ve been warned to stay indoors and preserve the cool. And, in the midst of it all, your home’s central air conditioner isn’t working.
If the thought of this doesn’t fill you with dread, nothing will. But don’t sweat, er, fret! You can take these steps to troubleshoot the problem with your system.
Check your thermostat — It’s possible that you or someone in your household may have inadvertently changed the settings, or that a recent power outage may have caused the date and time to go out-of-sync. If your home has a smart thermostat, you may be able to access diagnostic tools through the controlling smartphone app.

Change the air conditioner’s air filter every 60 to 90 days or more often if the manufacturer recommends it.
Change your air filter — The return air filters should be replaced regularly, typically every 60 to 90 days or more often if you have pets in your home. Leaving the filter in place for longer than the period specified by the manufacturer may cause dirt, dust, and allergens to clog the filter and decrease its efficiency.
Check your air ducts — If a duct is broken or detached, cool air could be escaping into your attic, crawlspace, or walls before reaching the vents in your rooms. While you may be able to repair or reattach ducts using—what else—duct tape, consider calling a professional to effect a permanent repair.
Clean your compressor — Remove any debris that may have gathered around the compressor, the part of the system located outside your home. Clean the coils with condenser coil cleaner, available at most hardware stores, and rinse with the garden hose. Make sure you follow the manufacturer’s instructions, including turning off the power to the unit before you clean it.
Check for a clogged condensation drain — Moisture that builds up inside the air conditioner during operation drains out of the unit through the condensation drain, usually to the outside of your home near the foundation. If this drain becomes clogged, it may cause your unit to work at a reduced capacity or stop working altogether. You can clear out the condensation drain with a thin wire brush, a wet/dry vacuum, or a combination of the two. If your air conditioner’s condensation drain gets clogged frequently, your air conditioner may require professional servicing.
Call a professional. If these other tips don’t get you from sweltering to shivering, contact an air conditioning contractor, licensed by the Department of Consumer Affairs’ Contractors State License Board. To find a licensed professional in your area, visit www.cslb.ca.gov.