No power from a window air conditioner usually traces to power supply, safety plug, control settings, or a failed component.
Your window air conditioner sits quiet, lights off, fan still. Before you assume the worst, work through a clean, safe sequence. The steps below start with zero-tool checks, then move to simple fixes any renter or homeowner can do, then show when to call a pro. Each action is short, specific, and ordered to save time.
Window Air Conditioner Not Turning On: Quick Checks
Start with the basics. Power issues and safety interlocks are the most common reasons a window unit refuses to start. Run this list from top to bottom.
| Likely Cause | What You See | Fast Check/Fix |
|---|---|---|
| Outlet Has No Power | No lights, no beep, fan won’t spin | Plug in a lamp or phone charger. If dead, inspect a tripped GFCI or the breaker. |
| LCDI/GFCI Plug Tripped | Reset button popped, status light off | Press RESET on the plug, then power the unit. If it won’t hold, stop and call an electrician. |
| Loose Power Cord | Intermittent power, unit flickers | Seat the plug firmly; skip adapters and extension cords. |
| Control Set To Fan/Dry Or Timer | Display on, no cooling | Switch mode to Cool, set temp below room temp, disable timers, raise fan to High. |
| Compressor Delay | Clicks, then pause with no cooling | Wait 3–5 minutes after power or mode change; many units delay start to protect the compressor. |
| Dirty Filter Or Frozen Coil | Weak airflow, icing, unit shuts off | Wash the filter. Let ice melt fully, then restart on Fan for 10 minutes. |
| Room Temp Too Low | Unit won’t start cooling at night | Cooling can lock out near 60–65°F. Try Fan only or wait for warmer room temps. |
| Tripped Breaker | One circuit off at panel | Flip the breaker fully off, then on. If it trips again, stop and get a licensed tech. |
| Failed Start Capacitor Or Board | Clicks, hum, then silent | DIY stops here. Schedule service for diagnosis and safe replacement. |
Safety First Before You Touch Anything
Unplug before handling filters, panels, or anything near the fan or coil. If the plug uses a test/reset block, treat it like a safety device: test monthly and stop if it won’t reset after you clear the cause. Water near outlets or a scorched plug means it’s time for a pro.
Step-By-Step: Bring A Silent Unit Back To Life
1) Confirm The Outlet And Circuit
Test the outlet with a phone charger or lamp. If both fail, check the panel for a tripped breaker. Flip it fully off, then back on. Older homes often share outlets on one small circuit, so a hair dryer or microwave can starve the air conditioner. Keep the unit on its own outlet when you can.
2) Reset The Safety Plug
Many room units ship with a plug that has TEST and RESET buttons. Press RESET, plug in, then press TEST; the reset button should pop. Press RESET once more for normal use. If the button won’t stay in or trips again right away, stop and have an electrician check for moisture or wiring faults.
3) Check The Control Settings
Make sure the mode is on Cool, not Fan or Dry. Set the temperature at least 4 degrees below the current room reading. Turn the fan to High. Turn off sleep mode, eco mode, and any timers until you confirm a normal start. Aim the remote at the sensor and replace weak batteries.
4) Respect The Built-In Delay
Most window units hold the compressor off for a short period after power returns or after you change modes. That delay protects the compressor from high pressure at restart. Wait 3 to 5 minutes and listen for the deeper hum that follows the fan.
5) Clear Airflow And Filter
Pop the front grille and slide out the filter. Wash with warm water and mild dish soap, rinse well, and let it dry. Clear leaves or lint from the outdoor fins. Leave at least a foot of space in front of the unit indoors and outdoors for smooth airflow.
6) Thaw A Frozen Coil
If you see ice on the indoor coil, unplug and let it melt. Speed this up by running Fan only with the front panel open. A clogged filter or blocked outdoor side often causes icing. After it’s dry, try again on Cool.
7) Stabilize The Install
A window unit needs to sit level side-to-side and tilt slightly to the outdoors for drainage. A tilt that’s too steep can trip float switches or wet electronics. Re-seat the side panels tightly to block warm air leaks that confuse the thermostat.
When The Plug Or Breaker Keeps Tripping
If the reset button or a GFCI outlet won’t hold, you may have water in the plug, damaged insulation, or a device fault. Dry the area, try a different outlet on a separate circuit, and skip extension cords. If it trips again, stop. Let a licensed electrician or HVAC tech find the fault instead of chasing it with repeated resets.
Diagnose By Sound, Light, And Timing
What Each Symptom Usually Means
Small clues tell you where to aim your next step. Use this quick map to narrow the field.
No Lights Or Beeps
Think power supply: dead outlet, loose plug, tripped breaker, or a failed safety plug.
Lights On, Fan Runs, No Cool
Mode setting, low temp setpoint, or a normal delay. After the delay, no change points to a failed capacitor or a sealed-system issue that needs a technician.
Clicks, Then Silence
That often marks the start relay trying to engage. Listen again after 3 minutes to see if the compressor catches. If not, stop short of part swaps and schedule service.
Display Codes
Many brands show simple codes for filter, sensor, or coil errors. Clear the filter alert after cleaning. If a sensor code returns, a tech can test the probe in minutes.
Care Tasks That Prevent The Next No-Start
Keep The Filter Clean
Wash monthly during peak season. A clean filter trims strain on motors and cuts the chance of icing.
Seal The Sides And Gaps
Use the included foam panels or a quality gasket kit. Air leaks waste power and feed warm air to the thermostat sensor.
Give It Breathing Room
Keep curtains, blinds, and furniture clear of the front grille. Outside, prune plants back so nothing blocks the condenser.
Mind The Thermostat Tricks
Don’t place lamps or a TV near the unit. Extra heat near the sensor fools the control and keeps the unit off balance.
What You Can Fix And When To Call
Plenty of no-start cases end with a simple reset, filter wash, or setting change. Past that point, safe work needs training and tools. Refrigerant handling, leak checks, and sealed-system repairs belong to certified technicians.
| Part Or Issue | DIY? | Next Step |
|---|---|---|
| Outlet, Breaker, Safety Plug | Yes | Test, reset, and replace damaged outlets or plugs through a licensed electrician. |
| Filter, Grille, Panels | Yes | Clean and seat panels; recheck airflow. |
| Remote Batteries, Settings | Yes | Replace batteries, set Cool, target temp, and fan speed. |
| Start Capacitor, Relay, Control Board | No | Call an HVAC tech for diagnosis and safe replacement. |
| Sensor Or Thermistor | No | Service visit; parts are low-cost but testing matters. |
| Refrigerant Leak Or Low Charge | No | Certified tech only; requires recovery gear and a leak check. |
Pro Tips That Save Power And Headaches
Keep the unit level to drain right. Set the thermostat to a comfortable number and leave it; rapid swings don’t cool faster. Use Low fan on muggy days to wring out moisture. These small habits cut wear and reduce the chance of mid-season failures.
When A Replacement Makes Sense
If the unit is older than a decade, needs a sealed-system fix, or still trips protections after the basics, a replacement can cost less over a few seasons. New models ship with better safety plugs and smarter controls, and many sip less power for the same cooling.
What To Tell The Technician
Share the model number, a photo of the data tag, and a short timeline: when the unit last ran, whether lights come on, and what the plug or breaker did. Mention any odd smells or water near the cord. That short list lets a tech arrive with the right parts.
Helpful Links You Can Trust
Many brands publish plug test steps and delay notes. Two helpful, reputable pages: