The AC runs all afternoon and the house stays warm and sticky. Call HVAC Sioux City and a licensed local cooling technician can find out why.
Five checks when your AC is not cooling
“Running but not cooling” is one of the most common summer calls in Sioux City, and a few of its causes are things you can fix yourself in minutes.
- Thermostat: set to Cool, fan on Auto (not On), set below room temperature.
- Filter: a clogged filter chokes airflow and can freeze the indoor coil.
- Outdoor unit: is the fan on top spinning? Is the coil caked with cottonwood fluff or grass?
- Ice: look at the larger copper line at the outdoor unit and near the furnace. Ice means stop: switch to Off with the fan On to thaw it.
- Registers and returns: open, and not blocked by furniture or rugs.
If the outdoor fan isn’t spinning, the line is iced, or nothing above changes things within an hour, call us. An AC not cooling in Sioux City in July is one of the busiest calls of the year, so the earlier the better.
What this repair covers
- Refrigerant leak search and recharge
- Frozen evaporator coils and their cause
- Dirty or blocked condenser coils
- Outdoor fan motors and capacitors
- Indoor blower speed and blower motor faults
- Compressor not running while the fan does
- Thermostat placement, settings and wiring
- Duct leaks and disconnected runs in attics
- Expansion valve and metering problems
- Humidity problems and drain issues
Why the AC runs but doesn’t cool
| Clue | Most likely cause |
|---|---|
| Outdoor fan spins, air inside is barely cool | Low refrigerant from a leak, or a compressor that isn’t running |
| Outdoor fan not spinning, unit hums | Failed capacitor or fan motor |
| Ice on copper lines | Restricted airflow or low refrigerant |
| Weak airflow from every register | Dirty filter, dirty coil, blower problem |
| Some rooms fine, others hot | Duct issues, closed dampers, long runs to upstairs rooms |
| Cool but clammy | Fan set to On, low charge, oversized system |
Urgent, or can it wait?
Call today during a heat wave if anyone in the house is elderly, very young, pregnant or has a health condition that makes heat dangerous, and move them to the coolest room, a basement, or somewhere air conditioned in the meantime. Call today too if the outdoor unit hums without spinning or the lines are iced; running it that way can damage the compressor.
It can usually wait a day if the house is warmer than you’d like but still under control and the system isn’t making new noises.
What the technician checks
Expect them to measure temperatures at the return and supply, check refrigerant pressures, test the capacitor and motors, look at the indoor coil and filter, and check the drain. That combination tells them whether the problem is refrigerant, airflow or electrical, and it often turns up a second issue that would have been the next call.
Preventing a repeat
- Change filters monthly in peak summer.
- Keep the outdoor coil clean and clear.
- Leave the fan on Auto for better humidity control.
- Have the system checked each spring.
AC not cooling in Sioux City’s older homes
A lot of Sioux City houses were built long before central air, and the ductwork was added later, often squeezed into closets and attics. That makes “AC not cooling” calls here a mix of equipment problems and airflow problems.
If the downstairs is fine and the upstairs is miserable, the equipment may be working and the air simply isn’t getting there: too few return grilles upstairs, long duct runs through a hot attic, or dampers set for winter. A technician can measure airflow room by room and tell you which it is. Sometimes the answer is balancing the system; sometimes a ductless mini split for the top floor is the practical fix.
If the whole house is warm, it’s more likely the equipment itself. Either way, tell us when you call whether the AC is not cooling anywhere or only in some rooms.
Questions about an AC that won’t cool
How much cooler should the air from my vents be?
A healthy central air system usually blows air somewhere around 15 to 20 degrees cooler than the air going into the return. If you hold a kitchen thermometer at a supply register and at the return grille and the difference is much smaller, the system is not removing enough heat: refrigerant, coil or airflow trouble is likely.
Why is my upstairs so much hotter than downstairs?
Heat rises, attics bake in the sun, and upstairs rooms are often at the end of long duct runs. Some difference is normal in older Sioux City two stories. A big or growing difference can point to leaky or undersized ducts, a weak blower or a dirty coil. Closing some lower floor registers part way can help push air upstairs.
Can low refrigerant just be topped off?
Refrigerant does not get used up, if it is low, it leaked somewhere. Adding refrigerant without finding the leak means it will be low again. A technician checks the charge, looks for the leak, and talks through the options for fixing it.
The AC cools during the day but not in the evening. Why?
Late afternoon is when your home has absorbed the most heat and the outdoor unit is fighting the hottest air. A system that is a little low on refrigerant, has a dirty condenser coil or is undersized falls behind then. If the house never catches up overnight, have it checked.
Why does the house feel clammy even though the AC is running?
Air conditioners remove humidity as well as heat. If the coil is not cold enough, or the fan runs constantly (fan set to On instead of Auto), moisture is not removed well and the air feels sticky. Set the fan to Auto, then call if it stays clammy.
Still warm inside? Call (555) 010-0142