Why is my AC running but not cooling the house?

The most common causes are a clogged filter, a blocked or dirty outdoor unit, a failed capacitor or fan motor, and low refrigerant from a leak. Check the thermostat is on COOL with the fan on AUTO, replace the filter and clear the outdoor unit first. If the air is still warm after 30 minutes, the fault is almost always a part that a licensed contractor needs to test.

Should I turn my AC off if it is not cooling?

Yes, if you see ice on the copper lines or the indoor coil, water leaking, a burning smell or a breaker that trips again after one reset. Running a frozen or short-cycling system can damage the compressor, which is the most expensive part to replace. If it is simply cooling poorly, you can leave it running while you check the filter and the outdoor unit.

How much does it cost to fix an AC that is not cooling?

It depends on the cause: a capacitor is $100 to $250, a refrigerant leak repair $200 to $1,500 and a compressor $600 to $2,500, according to HomeGuide’s 2026 national figures read on November 11, 2026. A diagnostic visit to find the cause usually runs $75 to $200.

Symptom guide

AC Not Cooling in Killeen: Causes, Checks and Costs

An AC that runs without cooling usually has an airflow problem (filter, coil, blocked outdoor unit), a failed start component (capacitor or contactor) or low refrigerant from a leak. Do the four checks below first; if the air is still warm after 30 minutes, it needs a licensed contractor.

Published November 11, 2026 · Figures and rules checked against the sources listed at the end of this page.

Four checks you can do safely

Thermostat. Set to COOL, fan on AUTO, set point a few degrees below the room temperature. Replace the batteries if the screen is dim or blank.
Filter. Hold it up to a light. If you cannot see through it, replace it.
Outdoor unit. Clear leaves, grass and anything stored within about two feet. Check that the fan on top is spinning.
Breakers. Find the breakers for the outdoor unit and the indoor air handler or furnace. If one has tripped and there is no burning smell or scorch mark, reset it once. If it trips again, leave it off.

Stop and turn it off if you see ice on the lines, water on the floor, a breaker that trips a second time, or you smell burning. Do not open panels or handle refrigerant.

Three of these causes have their own pages: a failed capacitor (the humming-outdoor-unit fault), a frozen coil and water leaking from the indoor unit.

The usual causes and what each costs to fix

Why an AC stops cooling (repair ranges are national, read November 11, 2026)
Cause	What you notice	The fix	Typical cost
Clogged filter or blocked outdoor unit	Weak airflow, long run times	A new filter; clear two feet around the unit	The price of a filter
Thermostat setting or dead batteries	Fan runs, no cooling; blank screen	COOL, fan AUTO, fresh batteries (the range is for replacing the thermostat itself)	$140 to $350
Failed capacitor	Outdoor unit hums, fan not spinning	Contractor repair	$100 to $250
Failed contactor	Outdoor unit silent while the indoor fan runs	Contractor repair	$200 to $450
Condenser fan motor	Unit runs hot, fan dead or grinding	Contractor repair	$200 to $700
Low refrigerant from a leak	Ice on the lines, cooling fades over days	Leak repair, then recharge	$200 to $1,500
Clogged condensate drain	Water in the pan; system shuts off	Drain line flush	$75 to $250
Dirty coil	Runs constantly, air only slightly cool	Coil cleaning	$100 to $400
Compressor failure	Breaker trips, loud start, warm air	Replace the compressor	$600 to $2,500

Source for repair ranges: HomeGuide, “How Much Does AC Repair Cost? (2026)”. National figures, not Killeen quotes.

Reading the symptoms

Blowing warm air

If the indoor fan is running and the outdoor unit is not, the fault is usually on the outdoor side: a capacitor, a contactor, a tripped breaker or a float switch that has shut the system off because the drain pan is full. If both are running and the air is still warm, suspect refrigerant or a compressor.

Ice on the lines or the coil

Ice means the coil is too cold, either because not enough air is passing over it or because the refrigerant charge is low. Switch the thermostat to OFF with the fan ON and let it thaw for a few hours, change the filter, then try again. If it refreezes, it needs a leak check.

Water around the indoor unit

The drain line that carries condensation outside has clogged, or the pan has cracked. Turn the system off so the leak does not spread. A drain line flush runs $75 to $250; a new pan $200 to $600.

Hums but will not start

A hum from the outdoor unit with no fan movement is the classic sign of a failed capacitor, one of the cheapest repairs on the system at $100 to $250. Turn it off rather than letting it keep trying.

Starts and stops every few minutes

Short cycling wears the compressor out. Causes range from a dirty filter to an oversized system or a failing control board ($150 to $700). If the system is older and this is a repeat problem, price a replacement alongside the repair: see repair or replace.

Who is allowed to fix it

You can change a filter, clear the outdoor unit and reset a breaker yourself. Repair work for the public requires a Texas air conditioning and refrigeration contractor license, so before anyone starts, look the company up with TDLR. If it cannot wait until morning, see emergency AC repair in Killeen.

Sources and dates

Every figure and rule above names where it came from and the date it was read. Price ranges are national guides; a written quote for your own system is the real number. For permit and license rules, the City and TDLR have the last word. Prices are rechecked at least every six months.

HomeGuide, “How Much Does AC Repair Cost? (2026)” — read November 11, 2026. National ranges, not Killeen quotes
Texas Occupations Code, Chapter 1302 (Air Conditioning and Refrigeration Contractors), §§1302.002, 1302.053, 1302.251 — read November 11, 2026