AC Won't Turn Off in Las Vegas: Causes and Fixes
Short answer: An AC that won't shut off in Las Vegas is usually caused by thermostat issues, dirty filters restricting airflow, low refrigerant from leaks, or a stuck contactor. During extreme heat (110°F+), systems may run continuously even when functioning normally. Check thermostat settings and batteries, replace dirty filters (Las Vegas dust storms clog them fast), and verify vents are open. If it still runs nonstop after these checks, schedule professional repair—continuous operation during peak heat can cause compressor failure and skyrocket energy bills.
Why AC Won't Turn Off Is Common in Las Vegas
Las Vegas's extreme desert climate creates unique conditions that cause AC systems to run longer than in milder climates. Summer temperatures regularly exceed 110°F, with peak afternoon heat reaching 115°F or higher. During these extreme conditions, even properly functioning AC systems may run continuously for 12-16 hours daily to maintain comfortable indoor temperatures. The combination of intense heat, frequent dust storms that clog filters in days rather than weeks, and long cooling seasons (May through October) means Las Vegas homeowners often experience nonstop AC runtime. Additionally, many Las Vegas homes have rooftop AC units exposed to direct sun, attic temperatures reaching 140°F+, and ductwork in unconditioned spaces that loses cooling capacity. These factors can make a system appear broken when it's actually struggling to keep up with extreme heat, or they can mask underlying issues like refrigerant leaks or airflow restrictions that become critical during peak demand.
Top Causes of a Constantly Running AC
- Thermostat issues: Set too low, misreading room temperature due to poor placement (near heat sources, in direct sunlight, or in hot hallways), dead batteries causing erratic behavior, or stuck in "Fan On" mode instead of "Auto"
- Dirty filters and restricted airflow: Clogged filters force the system to work harder and run longer (Las Vegas dust storms can clog filters in 2-3 days during summer), reducing cooling efficiency and preventing the system from reaching setpoint
- Low refrigerant from leaks: Common in older systems exposed to extreme heat, refrigerant leaks reduce cooling capacity, forcing the system to run continuously to try to reach temperature
- Faulty contactor or relay stuck closed: Electrical control component that fails in the "on" position, preventing the compressor from cycling off even when the thermostat isn't calling for cooling
- Undersized system for the home: System too small for square footage or heat load, common in Las Vegas homes where original systems weren't sized for current insulation or window upgrades
- Dirty evaporator or condenser coils: Desert dust coats coils faster than in mild climates, reducing heat transfer efficiency and forcing longer runtime
- Leaky ductwork: Attic ducts exposed to 140°F+ temperatures expand and develop leaks, losing cooled air before it reaches living spaces
- Blocked or closed vents: Closed vents or furniture blocking return/supply vents restrict airflow and prevent proper temperature control
- Extreme outdoor temperatures: During heat waves (110°F+), even properly functioning systems may run continuously—this is normal but increases wear and energy costs
AC Won't Turn Off Troubleshooting Checklist for Las Vegas Homes
Follow this systematic checklist before calling for service. Most nonstop runtime issues in Las Vegas can be resolved with these simple checks, saving time and money.
Step 1: Thermostat Check (30 seconds)
- Confirm thermostat is set to COOL mode (not HEAT or FAN only)
- Check if setpoint is unreasonably low (below 72°F)—raise to 74-76°F and wait 30 minutes
- Verify setpoint is at least 5°F below current room temperature
- Check if display is blank or dim—replace batteries (AA, AAA, or coin cell depending on model)
- Look for schedule locks or holds on programmable/smart thermostats that might override settings
- Note any error codes displayed on the thermostat screen
- Verify thermostat mode is "Auto," not "Fan On" (Fan On runs continuously)
Step 2: Air Filter Inspection (1 minute)
- Locate and remove the air filter (usually in return grille or air handler)
- Hold filter up to light—if you can't see light through it, replace immediately
- In Las Vegas, check filters monthly during summer (May-September), weekly after dust storms
- Use correct filter size—check existing filter for dimensions (e.g., 16x25x1)
- Install with airflow arrow pointing into the system
- Note: Dirty filters are the #1 cause of nonstop runtime in Las Vegas
Step 3: Vent and Airflow Check (2 minutes)
- Ensure all supply vents are open and unobstructed (check every room)
- Check return air vents for blockages (furniture, rugs, curtains, etc.)
- Verify no vents are completely closed (can cause pressure imbalances)
- Feel air coming from vents—should feel cool and strong, not weak or warm
- Check for ice on refrigerant lines or indoor coil (if visible through access panel)
- Listen for blower motor noise—should be steady, not grinding or squealing
Step 4: Outdoor Unit Inspection (2 minutes)
- Clear at least 2-3 feet of debris, vegetation, and obstructions around the unit
- Check for visible damage to fins or coils
- Verify outdoor fan is spinning when AC is running (should run continuously when compressor is on)
- Listen for unusual noises (grinding, buzzing, rattling)
- After dust storms, gently rinse coils with garden hose (power off first, let dry before restarting)
- Check if unit is in direct sun—consider adding shade structure (without blocking airflow)
Step 5: System Behavior Observation (ongoing)
- Note if system runs continuously without cooling (compressor and fan both running)
- Check if indoor temperature is actually dropping or staying the same
- Monitor energy bills for sudden increases (indicates efficiency loss)
- Record any unusual smells (burning, musty, chemical)
- Note time of day when nonstop runtime occurs (afternoon heat vs. all day)
- Check if certain rooms stay hot while others cool (indicates airflow or duct issues)
When to Call a Professional
If your AC still won't turn off after completing the troubleshooting checklist above, it's time to call a licensed HVAC technician. Here are specific situations that require professional service:
- System runs continuously for 24+ hours: Even during extreme heat, properly functioning systems should cycle off periodically. Nonstop operation indicates a problem.
- Indoor temperature not dropping: If the system runs constantly but the house isn't cooling, you likely have a refrigerant leak, compressor issue, or severe airflow restriction.
- Burning smell or electrical odors: Indicates overheating components, stuck contactor, or electrical fault—turn system off immediately and call for emergency service.
- Ice forming on coils or refrigerant lines: Low refrigerant or severe airflow restriction—system needs professional diagnosis and repair.
- Breaker trips when AC cycles: Electrical fault requiring immediate professional attention—do not reset repeatedly.
- Energy bills increased 50%+: Significant efficiency loss requiring professional diagnosis to identify root cause.
- System over 12 years old running nonstop: May indicate system is failing and replacement should be considered.
- Contactor or relay suspected: Electrical control issues require licensed technician—DIY electrical work is dangerous and illegal.
Emergency situations: If you smell burning, see smoke, hear loud grinding, or the breaker trips repeatedly, turn the system off at the breaker immediately and call for emergency service. In Las Vegas heat, these issues can quickly escalate to compressor failure or fire risk.
What a quality diagnostic should include
- Airflow measurement and temperature split testing
- Refrigerant pressure check and leak indicators
- Electrical testing for contactors and relays
- Thermostat and sensor verification
Emergency Red Flags
- Burning smell or buzzing from the panel
- Ice forming on the coil or refrigerant line
- Breaker trips when the AC cycles
Repair vs Replace Considerations
If the system is 12 to 15 years old and runs nonstop despite repairs, replacement may be the better long-term choice. Proper sizing and airflow testing are critical in Las Vegas.
What to Ask During Service
- Is the system properly sized for the home?
- Are coils and airflow within spec?
- Is the contactor or relay stuck closed?
Helpful resources for Las Vegas homeowners
- AC not blowing hard
- Air conditioner not cooling
- AC diagnostic visit
- AC breakdown warning signs
- AC repair
Las Vegas Nonstop Runtime Triggers
- West-facing rooms heating up after 3 pm.
- Dirty coils after dust storms lowering heat transfer.
- Return leaks pulling attic heat into the system.
- Thermostat in a hallway that runs warmer than bedrooms.
After-Visit Readings You Should Receive
- Temperature split and airflow measurements.
- Thermostat calibration and sensor checks.
- Refrigerant pressure readings if tested.
- Contactor/relay status and electrical notes.
Run-Time Reduction Plan
- Replace filters and confirm return airflow.
- Verify thermostat placement and settings.
- Seal return leaks to stop hot attic air.
- Schedule a tune-up before peak heat.
FAQs About AC Running Constantly
Can a dirty filter cause nonstop runtime?
Yes. It restricts airflow and slows cooling.
Is it bad to run nonstop in Las Vegas?
Yes. It raises bills and shortens system life.
What if the thermostat is wrong?
It can misread room temperature and keep cooling on.
Do you offer same-day repair?
Yes. Same-day service is available in most areas.
Do you serve Henderson and North Las Vegas?
Yes. We serve the entire Las Vegas Valley.
Should I reset the breaker if it trips?
Reset it once. If it trips again, leave it off and call for service.
Can low refrigerant cause nonstop runtime?
Yes. Low charge reduces cooling capacity and keeps the system running longer.
Need HVAC Service in Las Vegas?
The Cooling Company provides expert HVAC service throughout Las Vegas, Henderson, and North Las Vegas. Our licensed technicians deliver honest assessments, upfront pricing, and reliable results.
Call (702) 567-0707 or visit AC repair, maintenance, heating, or installation for details.
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Need AC Repair in Las Vegas?
If your AC won't turn off and basic troubleshooting hasn't resolved the issue, our licensed technicians can diagnose and fix the problem quickly. We specialize in:
- Thermostat calibration and replacement
- Refrigerant leak detection and repair
- Electrical control component repair (contactors, relays)
- Airflow optimization and ductwork repair
- System sizing evaluation and recommendations
- Emergency same-day service during heat waves
Call (702) 567-0707 or visit AC repair to schedule service. We serve Las Vegas, Henderson, North Las Vegas, and the entire Las Vegas Valley with 24/7 emergency service available.