AC Won't Turn On? What to Check Before You Call for Service

When your air conditioner will not turn on at all, it is easy to assume the worst. In many cases the problem is something simple, and checking a few things first can save you time and a service call.

1. Thermostat

Make sure the thermostat is set to COOL and the temperature is set a few degrees below the current room temperature. If the screen is blank, replace the batteries. If your thermostat is a smart thermostat, check that it is connected and that a schedule or eco mode is not overriding your setting.

2. Breakers

Go to your electrical panel and look for a tripped breaker for the air conditioner, the furnace or air handler, or both. A tripped breaker sits in the middle position or shows orange. Reset it once by pushing it fully off and then back on. If it trips again, do not keep resetting it. A breaker that trips repeatedly is warning you about an electrical problem that needs a technician.

3. The outdoor disconnect

Next to your outdoor unit there is a small box on the wall with a pull out block or switch. Make sure it is fully seated or switched on. Sometimes these get bumped by lawn equipment or left off after yard work.

4. The furnace or air handler switch

Your indoor unit has a power switch that looks like a regular light switch, usually on or near the unit. Make sure it is on. Also check that the furnace door panel is closed tightly. Most systems have a safety switch that will not let them run with the door off.

5. A full condensate drain

Many systems have a float switch that shuts the AC off when the condensate drain backs up. This protects your home from water damage. If you see water in the drain pan or your system shut off suddenly on a humid day, a clogged drain line may be the cause. See our post on AC water leaks for more.

When it is time to call

If you have checked all of the above and the system still will not start, the cause is likely a failed part such as a capacitor, contactor, control board, transformer, or a blown fuse. These involve high voltage and should be handled by a licensed technician.

Red Rock Mechanical serves homes and businesses in Oklahoma City, Shawnee, Bethel Acres, and Central Oklahoma. Call (405) 305-3085 or book online and we will get you cooling again.