AC Not Working? Reset Steps First, Repairs $172 to $664

National prices; add a $75 to $200 service call (HomeGuide, HomeAdvisor). HomeGuide figures are from its table.

Do this now: checks before you call

1. Hot house, someone at risk? The CDC says a fan can raise body temperature once indoor air is above 90 F; move people 65 and older, infants and anyone with heart disease or asthma somewhere cool (dial 2-1-1 to find one). Heat stroke signs such as a body temperature above 103 F or confusion mean call 911 (Ready.gov).
2. Thermostat. Bryant says to confirm it is set to Cool; set it a few degrees below room temperature and replace the batteries if the screen is blank.
3. Breaker panel. Bryant says all breakers should be ON. Reset a tripped AC or furnace breaker once. If it trips again, leave it off; see breaker keeps tripping.
4. Outdoor disconnect. Bryant describes it as a gray box near the outdoor unit, about 8 by 16 by 4 inches, and says it must be ON.
5. Furnace or air handler switch. If the indoor blower will not run, Bryant says to check that the furnace on/off switch, which looks like a light switch, is ON.
6. Filter. Bryant says an extremely blocked filter can shut down the outdoor unit. Replace it if it is clogged.
7. Leave the unit's panels closed. Carrier warns that AC capacitors store high-voltage electricity that can cause serious injury or death even when the power is disconnected.

How to reset an AC unit

To reset a central AC, turn the thermostat off, switch the AC breaker off for 30 minutes, then turn it back on and set the thermostat to Cool, says a reset guide from ServiceExperts.com, a national HVAC service company. Step by step:

1. Set the thermostat to Off.
2. Find the AC breaker in the electrical panel and switch it off.
3. Wait 30 minutes (ServiceExperts.com).
4. Switch the breaker back on, and check that the outdoor disconnect is ON (Bryant).
5. Set the thermostat to Cool, a few degrees below the room temperature. ServiceExperts.com says the system should start within seconds and the vents should blow cool air.

If the breaker trips again, or the AC still does not run after a reset, stop resetting it and call. A breaker that keeps tripping points to a fault the technician needs to find.

Where is the reset button on an AC unit?

Some outdoor units have a small red reset button, usually on or near the condensing unit and sometimes under a panel marked Reset, ServiceExperts.com says; check the owner's manual, because many units have none. Its steps: thermostat off, breaker off, hold the button for 3 to 5 seconds, breaker on, thermostat to Cool. If reaching the button means removing a panel, do not: Carrier warns the capacitor inside can hold a lethal charge with the power off.

Why is my AC not working? The common causes

An AC that will not turn on most often has a thermostat problem, a tripped breaker, a failed capacitor, low refrigerant or a safety switch that has shut it off, Carrier says. HomeGuide adds that when a fuse blows, the outdoor unit turns off. What the system is doing narrows it down:

• Nothing at all: power. The thermostat, the breaker, the disconnect or a blown fuse.
• Indoor fan on, outdoor unit off: the disconnect, a fuse, a capacitor or a contactor. Carrier lists a failed capacitor among the reasons a compressor will not start; see AC capacitor replacement.
• Outdoor unit hums or clicks without starting: Carrier lists a unit that hums but does not start as a capacitor sign; HomeGuide lists clicking and repeated start attempts among compressor failure signs. See AC compressor repair.
• It starts, then shuts off: a very clogged filter (Bryant), ice on the coil (see AC freezing up), or a safety switch. If water is pooling at the indoor unit, see AC leaking water.

AC stopped working after a power outage

A power surge or outage can trip the AC's breaker, and the unit will not run until it is reset, ServiceExperts.com says. Run the reset steps above once. If the AC still will not start after power returns, call a technician to test the electrical parts; HomeGuide prices a capacitor at $100 to $250 and a circuit board at $150 to $700.

Is an AC that will not turn on an emergency?

An AC that will not turn on is an emergency when the heat puts someone at risk: the CDC says people 65 and older, infants and young children, and people with asthma or heart disease are at higher risk, and that a fan can raise body temperature once indoor air is above 90 F. Act now if:

• Someone shows heat stroke signs such as a body temperature above 103 F, hot red dry skin or confusion: call 911 (Ready.gov).
• You smell burning or see smoke from the unit or the panel: get out and call 911.
• The breaker trips again right after a reset, or HomeGuide's warning signs show up: burned wiring near the compressor, blown fuses.
• The house is climbing toward 90 F with vulnerable people home. Dial 2-1-1 to find a cooling place, then call for repair.

Emergency HVAC repair has after-hours rates, and local pages cover Phoenix, Houston and Miami.

How much does it cost to fix an AC that will not turn on

Most AC repairs cost $172 to $664, an average of $417, in HomeAdvisor's 2026 guide, and the parts behind a dead AC are usually at the low end. HomeGuide prices a capacitor at $100 to $250, a contactor at $200 to $450, a fuse or breaker at $75 to $300, a relay at $100 to $300 and a thermostat at $140 to $350. A compressor is the expensive outcome: $1,200 to $2,800 (HomeAdvisor). Both guides put the service call at $75 to $200, and HomeAdvisor says most companies apply it to the repair.

For a big repair on an older unit, HomeGuide and HomeAdvisor both suggest replacing when the AC is over 10 years old, uses R-22, or the repair cost times its age passes $5,000. See AC replacement cost.

Who to call when the AC is not working

Call an HVAC company for the AC itself; call an electrician if the problem is the panel, such as a breaker that will not stay on for other circuits too (see electrical repair). Before you book, ask:

• What is the service call fee, and does it go toward the repair?
• Is there an after-hours rate? HomeAdvisor and HomeGuide put emergency labor at $160 to $250 an hour.
• Will the technician test the capacitor and contactor before calling it a compressor failure? PickHVAC advises it.
• What is your license number, and can I see proof of insurance? Check the license with your state board.

If the AC runs but the air is warm, see AC not cooling; every fix is priced on AC repair. Local AC repair pages include Phoenix, San Antonio and Orlando. The HVAC repair hub covers heating too, and home repair costs compares trades.

Calls go to an independent company that serves your area and takes this kind of job. Ask for its license number and proof of insurance yourself. Some companies take emergency calls; hours vary. How calls work.