Why is my air conditioner running but not cooling my house?
When an air conditioner runs but does not cool, the cause is almost always one of five things: a clogged air filter, a frozen evaporator coil, a dirty outdoor condenser, a failed capacitor, or low refrigerant from a leak. Start by checking the filter and looking for ice on the copper lines. If the filter is clean and there is no ice, the problem is electrical or refrigerant related, and it needs a technician.
What "running but not cooling" actually means
Your system has two jobs. The indoor blower moves air. The outdoor unit removes heat from that air and dumps it outside. When you hear the system running but feel warm air at the vents, the blower is doing its job and the heat removal side is not.
That narrows the problem down fast. You are not looking for a dead system. You are looking for the one part of the heat transfer chain that broke.
What should I check before calling anyone?
Two checks take about five minutes and solve a real share of the calls we get in July and August.
- Check the air filter. Pull it out and hold it up to a light. If you cannot see light through it, it is choking your airflow. A starved system cannot move heat, and it will eventually freeze up. Replace it and give the system an hour.
- Look for ice. Open the closet or look at the copper lines running into the outdoor unit. Frost or a block of ice means the coil froze. Turn the cooling off, leave the fan on, and let it thaw for a few hours. Running a frozen system damages the compressor.
If the filter was filthy or the coil was iced, you found a symptom, not the root cause. Something restricted the airflow or dropped the refrigerant pressure to get there.
What are the five causes we find most often?
- Clogged filter. The cheapest fix and the most common. In dusty Kansas summers, a one inch filter can load up in 30 days.
- Frozen evaporator coil. Caused by restricted airflow or low refrigerant. The ice blocks air completely, so output drops to nothing.
- Dirty outdoor condenser. Cottonwood, grass clippings, and dryer lint pack the outdoor coil. The system cannot reject heat into 100 degree air when the coil is blanketed.
- Failed run capacitor. The capacitor gives the compressor and fan motor the jolt they need to start. When it weakens, the fan may spin while the compressor never engages. You get airflow with zero cooling. This is one of the most common July failures we see.
- Low refrigerant from a leak. An air conditioner is a sealed loop. It does not use up refrigerant. If the charge is low, there is a hole somewhere, and topping it off without finding the leak just buys a few weeks.
How do I tell the difference?
The pattern of what is running tells you a lot.
- Indoor fan runs, outdoor fan runs, no cold air, no ice: likely a dirty condenser or a refrigerant problem.
- Indoor fan runs, outdoor unit hums but the fan does not spin: almost always a capacitor.
- Weak airflow at every vent plus ice on the lines: filter or blower restriction first.
- Cools fine in the morning, quits in the afternoon: the system is undersized or overloaded for a 100 degree day, or the charge is marginal.
What does the repair usually cost?
We charge a flat $129 residential diagnostic. That covers the trip and the diagnosis on any brand of AC, and we tell you the repair price before we start the work. Visits after 6pm on weekdays or anytime on a weekend are $179.
From there, our published repair prices for the parts behind this problem are:
- Single run motor capacitor: $160 to $200
- Dual run motor capacitor: $200 to $300
- Air conditioner contactor: $250 to $350
- Condenser fan motor: $650 to $1,250 and up, based on manufacturer pricing
- Failed thermostatic expansion valve: $800 to $1,900
A capacitor is a same visit fix. A refrigerant leak takes a leak search first, because sealing the hole is the only repair that lasts.
When does this become an emergency?
Heat is a health risk for infants, older adults, and anyone with a heart or breathing condition. If the indoor temperature is climbing past the mid 80s and someone in the house is vulnerable, do not wait until morning. Our phone is answered 24 hours a day, seven days a week, by a real person.
Otherwise, shutting the system off overnight and calling first thing protects the compressor and saves you the overtime rate.
What to do next
Change the filter, clear two feet of space around the outdoor unit, and give the system an hour. If the vents are still warm, the next step is a diagnostic. We have been fixing these calls across Leavenworth, Lansing, Basehor, Shawnee, and the wider Kansas City metro for over 17 years, and we hold a 4.8 star rating across more than 600 Google reviews.
Frequently asked questions
Why is my AC running but not cooling my house?
The five most common causes are a clogged air filter, a frozen evaporator coil, a dirty outdoor condenser coil, a failed run capacitor, and low refrigerant from a leak. Check the filter and look for ice on the refrigerant lines first. If both are fine, the fault is electrical or refrigerant related and needs a technician with gauges.
Should I turn my AC off if it is not cooling?
Yes, in most cases. If you see ice on the coil or the lines, switch cooling off and run the fan only so the ice can melt. Running a frozen or low charge system can send liquid refrigerant back to the compressor, which is the most expensive part to replace.
Can a dirty air filter stop an AC from cooling?
Yes. A loaded filter restricts airflow across the evaporator coil. Less air across the coil means less heat removed, and the coil surface can drop below freezing and ice over, which blocks airflow completely. In dusty Kansas summers a one inch filter can clog in about 30 days.
How much does it cost to find out why my AC is not cooling?
Mr. Breeze charges a flat $129 residential diagnostic during normal hours, or $179 after 6pm on weekdays and anytime on weekends. That covers the trip and the diagnosis on any brand, and we quote the repair before starting work.
Does my AC need refrigerant every year?
No. An air conditioner is a sealed system, so it never consumes refrigerant during normal operation. If the charge is low, there is a leak. Adding refrigerant without repairing the leak is a temporary fix that costs more over a season than finding the hole.
How we know this
This guidance comes from what our technicians find on real service calls across Leavenworth, Shawnee, and the Kansas City metro. Prices shown are our own published rates. Anything that depends on your specific equipment is called out as something we confirm on site.
Licensed, insured and bonded mechanical contractors. EPA certified technicians.
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Still not sure what you are dealing with?
Tell us what the system is doing and we will tell you what it means. A real person answers the phone 24 hours a day, and we quote the repair before we start work.
Serving Leavenworth, Shawnee, and the Kansas City metro since 2009. Licensed, Insured & Bonded Mechanical Contractors.