Five groups cover the causes of an AC not cooling in Las Vegas, NV: airflow, electrical parts, refrigerant, drainage and controls. Go through them in order, and if the system still does not cool, use Call Now and an independent HVAC contractor serving 77 ZIP codes around Las Vegas will answer.
Airflow: the first thing to check
- Closed or blocked registers and returns
- Dirty evaporator coil or condenser coil
- Crushed or disconnected ductwork
- Dirty or clogged filter
- Failing blower motor or a slow fan
Electrical causes
- Failed control board or transformer
- Wiring or thermostat faults
- Pitted or stuck contactor
- Tripped breaker or blown fuse
- Failed run or start capacitor
Refrigerant and compressor
A low charge makes the AC blow slightly cool air and may freeze the coil. A failing compressor may hum, trip the breaker or run without cooling. Both need a certified technician under EPA Section 608.
Drainage and safety switches
A clogged condensate drain can trip the float switch, which turns off the system to prevent water damage. Clearing the drain and resetting the switch restores operation, and a cleanout helps prevent repeats.
Symptom to cause
| What you notice | Common cause |
|---|---|
| Warm air from vents | Low refrigerant, failed compressor or a dirty coil |
| Weak airflow | Dirty filter, blower or duct problem |
| Outdoor unit not running | Capacitor, contactor, breaker or safety switch |
| Ice on lines | Airflow or refrigerant problem |
| Water around the unit | Clogged drain or frozen coil melting |
Ducts, airflow and comfort
Even a sound system leaves hot rooms when ducts leak, returns are undersized or registers are blocked, because comfort depends on airflow as much as capacity. These problems show up when a technician measures static pressure and airflow instead of only refrigerant pressures.
A checklist for this week
- Inspect the drain line outlet and the area around the air handler for water
- Test the thermostat and schedule
- Write down any noises or smells
- Clear the outdoor unit of debris
- Book a tune-up if it has been more than a year
- Check supply and return registers
- Replace the filter and note the date
Myths and facts
- Myth: refrigerant is used up. Fact: low refrigerant means a leak.
- Myth: maintenance is optional. Fact: dirty coils and weak capacitors cause many summer failures.
- Myth: set the thermostat very low to cool faster. Fact: the AC cools at a steady rate and just runs longer.
- Myth: a bigger AC is always better. Fact: oversizing causes short cycling and humidity problems.
- Myth: closing vents saves energy. Fact: it raises duct pressure and can cause leaks and noise.
HVAC terms explained
- Condenser coil: the outdoor coil where heat is released
- Evaporator coil: the indoor coil where refrigerant absorbs heat from the air
- Condensate drain: the line that carries moisture out of the house
- Superheat and subcooling: readings that show whether the refrigerant charge is correct
- Contactor: the switch that sends power to the outdoor unit
- Static pressure: a measure of airflow resistance in the ducts
- EPA Section 608: the certification required to handle refrigerants
What shapes the written scope
Do not judge an AC job by how the call sounds, since two similar complaints can lead to very different work. Look for a written scope that states the technician's findings and the factors that applied.
Ask the provider to separate the diagnostic from the repair, and to list any parts, labor or follow-up that are not included.
- The age, tonnage and refrigerant type of the system
- Whether the ductwork, return air or thermostat contributes to the problem
- Warranty status of the parts and whether the equipment is registered with the manufacturer
- Whether the fault is an electrical part, an airflow problem, a refrigerant leak or a drainage problem
- Access to the air handler in the attic or closet and to the outdoor unit
Safety and rules to know
High-voltage electricity, pressurized refrigerant and moving parts all come together in an air conditioner. Leave electrical panels closed, never bridge contactors, and do not add refrigerant yourself. A capacitor may still hold a charge once the power is off.
Certification under EPA Section 608 is required in the United States for anyone buying or handling refrigerant, which must be recovered instead of vented. Request the technician's certification and confirm the contractor's licence through Nevada State Contractors Board (C-21 Refrigeration and Air Conditioning).
Questions to ask before approving a repair
- How old is the system and which refrigerant does it use?
- Will you give me the findings and the scope in writing before work starts?
- What does the repair warranty cover and for how long?
- What are my options: repair now, repair and monitor, or replace?
- What failed, how did you confirm it and can you show me the part or the reading?
Prepare your Las Vegas home before the technician arrives
- Check that the outdoor disconnect and the breaker are on, but do not open electrical panels
- Replace or check the filter, and clear furniture from the return grille and the air handler
- Set the thermostat to cool and note what it shows and what the house temperature is
- Write down the sounds, smells, leaks or ice you have noticed, and when
- Clear weeds, leaves and debris from around the outdoor unit
When to call a professional
Pick up the phone if the system will not start, if ice or water shows up, if the same problem comes back after your own checks, if you hear grinding or banging, or if anyone at home is vulnerable to heat or cold. Call Now at the top of the page puts you through once you describe what the system is doing: an independent HVAC contractor covering your ZIP code confirms the address and diagnoses the system in person.
What this means for a home in Las Vegas
Extreme desert heat with summer highs above 105 degrees and long cooling seasons; attics are far hotter than the air outside. Monsoon moisture in July to September adds humidity spikes.
Nevada contractors are licensed by the Nevada State Contractors Board; refrigeration and air conditioning is the C-21 classification. Dust and sun exposure clog and age condenser coils; many systems last about 10 to 15 years in extreme heat. Use these local details when you compare advice, and ask any technician how they apply to your system and your house.
Getting help in Las Vegas and nearby cities
Through Air Conditioning Installation Las Vegas, you can reach independent HVAC contractors serving 77 ZIP codes in Las Vegas, Nevada: 89101, 89102, 89103, 89104, 89105, 89106, 89107, 89108, 89109, 89110. Requests also go to providers in North Las Vegas, Henderson and Boulder City, and coverage is checked for each address individually.
Start with Call Now at the top of the page and say what you have found. The contractor checks your address, looks over the system and gives you the scope in writing.
Keep reading
Related pages for Las Vegas homeowners: How to Lower Cooling Bills; Summer HVAC Checklist for Las Vegas; SEER2 Explained for Las Vegas Homeowners; Frozen AC Coil: Why It Happens and What to Do. For the area list, see the service areas page.
Common questions about AC not cooling? 12 causes and fixes
Why is my AC blowing warm air?
Low refrigerant, a failed compressor, a dirty coil or a wrongly set thermostat are the common causes.
Can a dirty filter stop my AC from cooling?
Yes. It reduces airflow and can freeze the coil.
What if the outdoor unit does not start?
Check the breaker and the disconnect and call for service if it still does not start.
Does the thermostat matter?
It can; the system may stop because of dead batteries or incorrect settings.
Is it worth repairing?
It varies with the cause, how old the system is and what the warranty says.
Can low refrigerant be topped up?
Not until the leak has been found and repaired.