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AC Blowing Warm Air in Las Vegas: Wrong Mode vs a System That Is Not Cooling
Warm air from the supply vents feels like a broken air conditioner. Sometimes it is. Sometimes the thermostat is still on Heat, a heat pump is on Emergency Heat, or the fan is on with no cooling call.
This page is the warm-air sort. If Cool is set correctly, the outdoor unit is running, and the air is still barely cool, use the deeper no-cool checks: AC running but not cooling.
Colton Air Conditioning schedules these calls Monday–Friday, 8am–5pm.
Sort it in this order
1. Thermostat mode
Confirm the mode says Cool, not Heat, Off, or Fan. Set the temperature a few degrees below the room temperature. Fan usually Auto.
A blank screen is often dead batteries — see thermostat not working.
2. Heat pump settings
If you have a heat pump, leave everyday cooling on Cool. Emergency Heat / Auxiliary is electric strip heat. It can blow warm or hot air even in summer if someone left it there. Switch back to Cool (or Heat in winter for normal heat-pump heating) and wait a few minutes.
3. Ice on the lines
If the copper lines are iced, shut cooling off and thaw. Running Cool while iced makes warm air worse later — frozen AC coil.
4. Filter once
Replace a gray or collapsed filter. Restricted airflow can push a coil toward freeze-up or a weak temperature split.
5. Then decide which problem you have
| What you see after mode is Cool | Treat it as |
|---|---|
| Outdoor unit silent, warm blow | Start/capacitor/power or thermostat call — not “add Freon” first |
| Outdoor fan on, air still warm | Running but not cooling — [full checklist](/guides/ac-running-not-cooling) |
| Warm then cold cycling oddly | Short cycling or freeze/thaw loop |
| Only one floor warm on a two-system house | That floor’s system — [Summerlin two-system notes](/areas/summerlin) if that is your layout |
Why this is not the same page as “running but not cooling”
“Running but not cooling” assumes the equipment is trying to cool and the air is still warm. “Blowing warm air” also catches wrong mode, emergency heat, and fan-only. Starting there saves a service call that was a thermostat setting.
Once Cool is confirmed and the outdoor system is active, do not stay on this page — use the not-cooling guide for coils, charge, capacitors, and temperature split.
What not to do
- Do not keep Cool on while the lines are iced.
- Do not leave Emergency Heat on as a summer “fix.”
- Do not accept a full-system quote from the driveway with no panel opened.
- Do not reset a tripped breaker all afternoon — breaker trips.
Related: AC repair Las Vegas, HVAC second opinion.
When to call
Call when Cool is set correctly, the filter is fine, there is no ice (or it has thawed), and the vents are still warm, the outdoor unit will not start, or the breaker will not stay on.
Have ready if you can: heat pump or straight cool if you know, what the thermostat mode shows, and whether the outdoor fan is spinning.
Hours are Monday–Friday, 8am–5pm. If the house is hot outside those hours, fix mode and ice first, then call when we are open.
FAQ
Can the AC blow warm air if the thermostat is on Heat by mistake?
Yes. That is one of the first things to rule out in shoulder seasons.
Why would a heat pump blow warm air in summer?
Emergency / auxiliary heat is electric heat. If that mode was left on, you can get warm air while paying to heat the house.
Warm air but the outdoor unit is running hard — same as this page?
Use AC running but not cooling for that pattern.
Does warm air mean the compressor is dead?
Not always. Wrong mode, ice, filter, capacitor, dirty outdoor coil, and low charge can all feel the same from the hallway.
What hours can I reach Colton?
Monday through Friday, 8am to 5pm.
Cool is set and the vents are still warm? Call Colton Air Conditioning at (702) 738-6976 Monday–Friday, 8am–5pm. Tell us the thermostat mode and whether the outdoor unit is running. We will tell you if we can see it.
Colton Air Conditioning · Las Vegas Valley residential HVAC · Monday–Friday 8am–5pm
Call (702) 738-6976 or Book Online. License 0092120. Hours Monday through Friday, 8am to 5pm. Saturday and Sunday are closed.
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