AC Stopped Working? 7 Things to Check Before You Call

Ground Rules: Look, Switch and Swap, Never Open

Everything here is something you can safely look at, switch or replace. None of it means taking a panel off the condenser or the air handler: the condenser runs on 240 volts, and its capacitor can hold a charge after the breaker is off. Photos of the thermostat, the filter and the outdoor data plate give the technician a head start.

Most 1990s and 2000s two-story homes in Matthews, Stallings and Mint Hill have a split system: a condenser or heat pump beside the house, and an air handler or furnace in the attic, a closet or the crawl space. Find both halves first.

Checks 1 to 3: Thermostat, Breaker and Outdoor Disconnect

Check 1: The thermostat

Homeowner switching an upstairs hallway thermostat to Cool mode in a Matthews, NC home

Confirm the mode reads Cool, the setpoint is a few degrees below room temperature, and the fan is on Auto. A blank screen on a battery model usually means dead batteries; on a wired model it means lost 24-volt power from the air handler, which points to Check 2 or Check 5. Smart thermostats may be running an away mode or a utility demand-response event, so check the app history. After a setting change, many systems wait about five minutes before the compressor restarts.

Check 2: The breaker, reset once

Homeowner looking at a tripped AC breaker in a garage electrical panel in a Matthews, NC home

At the main panel, usually in the garage, look for breakers labeled AC, condenser, heat pump, air handler or furnace. A tripped one sits in the middle position. Push it firmly to off, then back on. Attic air handlers often have a light-style service switch near the cabinet; make sure it is on.

Check 3: The outdoor disconnect

Gray outdoor AC disconnect box on the brick wall beside a condenser at a Matthews, NC home

The gray box on the wall by the outdoor unit is the disconnect. Landscapers and pressure-washing crews sometimes switch it off and forget. If you know it was turned off, turn it back on. If the pull-out block is missing or the box looks scorched or rusted, leave it alone and tell the dispatcher.

Check 4: The Air Filter

Pollen-clogged pleated air filter held next to a clean filter at a return grille in a Matthews-area home

Pull the filter at the return grille or beside the air handler. If you cannot see light through it, it is choking airflow across the indoor coil, the most common road to a frozen coil in a humid Carolina summer. Replace it.

The yellow pine pollen that coats cars across Mecklenburg and Union counties in late March and April loads a one-inch filter fast, so homes near wooded lots may need a new one monthly into May. If some rooms always run warm even with a clean filter, leaky or crushed ducts may be involved; see ductwork repair and humidity control.

Check 5: The Float Switch and Condensate Drain

Float switch clipped to a water-filled secondary drain pan under an attic air handler in a Matthews-area home

On a muggy July day an air conditioner pulls gallons of water out of the indoor air, and it leaves through a PVC drain line. When algae clogs the line, a float switch shuts off the cooling so the overflow does not come through your ceiling.

With an attic air handler, look at the secondary pan under the unit and the small float switch clipped to the pan or drain line. Standing water or a raised float means the switch did its job. A brown ring on the upstairs ceiling is the same problem, one step further along.

• Do not tape the float down or bypass its wires.
• Do turn the system off and put towels or a bucket under any drip.
• Do mention the water when you call; clearing the drain is routine on an AC repair visit in Matthews.

Check 6: Ice on the Coil or the Big Copper Line

Ice-covered insulated copper suction line entering an outdoor AC unit at a Matthews, NC home in summer

Ice on the larger insulated copper line at the outdoor unit, or water pooling around the air handler, means the indoor coil froze, usually from a clogged filter, a blower problem or a refrigerant leak.

1. 1Set the thermostat to Off and the fan to On.
2. 2Let the fan run until the ice is gone, which can take several hours in a damp attic.
3. 3Put towels or a shallow pan where the melt water may collect.
4. 4Install a clean filter, then switch back to Cool. If ice returns within a day, turn cooling off and call.

Never chip or scrape ice off the coil or the copper. The tubing is thin, and a punctured coil is one of the more expensive repairs on any system.

Check 7: The Outdoor Unit

Pine straw and pollen built up on an outdoor AC condenser beside a brick home in Stallings, NC

• Pine straw or clippings packed against the fins. With the disconnect off, pull debris away by hand and keep two feet clear. A gentle garden-hose rinse, never a pressure washer, removes pollen.
• A hum with the top fan standing still. Usually a failed capacitor or fan motor. Turn cooling off so the compressor does not overheat, then call.
• Clicking or buzzing with nothing starting. Often a pitted contactor or weak capacitor. Also a call.
• Both fans running but warm air inside. Possibly a refrigerant or compressor problem, which needs an EPA Section 608 certified technician.

Two Things That Look Like a Dead AC but Are Not

Right after a power outage

When the power comes back after a summer storm, many systems wait a few minutes before the compressor restarts, and some thermostats reboot to a default schedule or to Off. Give it five to ten minutes, confirm the thermostat still says Cool with the right setpoint, and only then start the checklist. If the outdoor unit hums or stays silent after that, a surge may have taken out a capacitor, contactor or board fuse, which is a job for a technician.

Closed registers and blocked returns

A room that suddenly stops cooling after a furniture move or a new rug often has a closed supply register or a return grille hidden behind a couch. Shutting too many registers to push air upstairs can also starve the indoor coil of airflow and freeze it. Open the supplies, clear 12 inches in front of every return, and see whether cooling recovers before deciding the AC itself has failed.

When a Check Becomes a Service Call

Treat that last row as an emergency. Our 24/7 emergency AC repair line is answered by a live person, and we confirm timing on the call based on the nearest available technician.

What to Tell the Dispatcher

Say which checks you did, whether each fan runs, any sound, smell or water, and whether anyone at home is sensitive to heat. Every HVAC technician we send is licensed and insured in North Carolina. The technician diagnoses first and gives you a written price before work starts.

HVAC service in Stallings is about 5 to 10 minutes from Matthews; actual timing depends on the nearest available technician and is confirmed on the call. Wondering if an older unit is worth fixing? Read how AC repair cost is set in Matthews and whether to repair or replace a 15-year-old system.

The Bottom Line When the AC Quits

Work the seven checks in order, give a system a few minutes after any outage, and stop the moment something points past a switch or a filter: a second breaker trip, ice, water through a ceiling, a burning smell or a humming outdoor unit. That is when AC repair from a licensed technician saves money instead of costing it. If it is late, hot, or someone at home is struggling with the heat, call (321) 478-0693; a person answers 24/7.