My AC Stopped Working in Northern Virginia: What to Check First and What to Do Next

Published by Fairfax Mechanical · fairfaxmechanical.co · July 2026 · Emergency service: fairfaxmechanical.co/contact

It's 96°F outside. Your AC is completely off. Before you wait on hold for emergency service, there are five things worth checking — because the most common causes of a complete shutdown are things you can address yourself in under five minutes.

Step 1: Check the Circuit Breaker

The most common cause of a complete AC shutdown. Go to your electrical panel. Look for the breaker labeled "AC" or "Air Conditioner." A tripped breaker sits in the middle position.

If tripped: Push fully to OFF, wait 30 seconds, push firmly to ON. Set thermostat to Cool, 3–4°F below current temp. Wait 3 minutes. If the breaker trips again immediately — stop resetting it. Call a technician. A repeatedly tripping breaker indicates an active electrical fault.

Step 2: Check the Thermostat

Confirm it's set to COOL (not HEAT or OFF), fan to AUTO, and setpoint lower than room temp. If battery-powered, replace the batteries — a thermostat with dead batteries won't communicate with the AC regardless of settings.

Step 3: Check the Air Filter

A severely clogged filter can trigger an automatic safety shutdown by freezing the evaporator coil. If the filter is packed with debris, replace it. Then set to FAN ONLY for 30–60 minutes to thaw any ice before switching back to COOL. Running COOL mode on a frozen coil can damage the compressor.

Step 4: Check the Drain Pan Float Switch

Many HVAC systems shut off automatically when the condensate drain pan fills with water (clogged drain line). Find the drain pan beneath the indoor unit. If there's standing water — use a wet vac to clear it. The float switch will reset when the pan is dry and the system can restart. The underlying drain blockage should be professionally cleared.

Step 5: Check the Outdoor Unit

Is it running? Is the fan spinning? Is there ice on the refrigerant lines? Ice on the lines = frozen coil = run FAN ONLY for 1–2 hours before attempting to restart in COOL mode. Outdoor unit completely off with a humming sound = likely failed capacitor = call a technician.

What NOT to Do

• Don't reset a tripping breaker more than once — repeated resets on a faulty circuit can cause wiring damage or fire

• Don't run COOL mode on a frozen coil — damages the compressor

• Don't add refrigerant yourself — requires EPA 608 certification; low refrigerant means there's a leak that must be located first

• Don't pour water into the drain pan — adds to the problem the float switch is already reacting to

How to Slow Heat Gain While Waiting

• Close all blinds and shades on south- and west-facing windows immediately

• Close interior doors — keep people in the coolest room

• Run ceiling fans counterclockwise (summer mode)

• Avoid heat-generating appliances — oven, dishwasher, dryer

• Move to the lowest level if possible — basements run 5–10°F cooler than upper floors

What to Tell the Dispatcher

• System make and model (data plate on outdoor unit)

• Approximate system age

• Whether outdoor unit runs at all; any sounds before it stopped

• Steps already checked (saves diagnostic time)

• Any medically vulnerable individuals in the home (legitimate priority factor)

• Refrigerant type if known (R-410A for post-2010; R-22 for older systems)

Most Common Emergency Failure Causes

Fairfax Mechanical provides same-day emergency AC service across Fairfax, Reston, Herndon, McLean, Vienna, Falls Church, Arlington, Alexandria, Centreville, and Burke. Schedule immediately at fairfaxmechanical.co/contact.