Quick answer
When an AC runs but the house won't cool, the cause is usually one of a handful of things: a clogged filter choking airflow, a dirty or iced-over coil, a low refrigerant charge from a leak, a tripped breaker, or a thermostat problem. A few are simple checks you can do yourself; the rest need a technician, because guessing at refrigerant or electrical issues makes them worse.
- Start with the easy checks: thermostat set to cool, breaker on, and a clean filter.
- A frozen evaporator coil or iced lineset means shut it off and call, running it makes it worse.
- Warm air plus a hissing or bubbling sound often points to a refrigerant leak, not a low charge to 'top off.'
- An outdoor unit that won't start can be a capacitor or contactor, common and repairable.
- If basic checks don't fix it, get a diagnosis before parts get damaged.
When this question matters
It's a hot afternoon, the system is clearly running, but the house keeps drifting warmer. Before you call anyone it helps to know which problems you can rule out in five minutes and which ones mean 'turn it off and get help.' Knowing the difference saves you a service fee on a dirty filter, and saves your compressor from damage when the real issue is ice or low refrigerant.
Why these problems cluster in our climate
North Texas runs its air conditioners hard for months, so the small neglects show up fast. Filters clog quicker when the system runs constantly, coils foul in our dust and pollen, and a slow refrigerant leak that might hide for years up north reveals itself in a single brutal week here. Most 'my AC stopped cooling' calls trace back to airflow or charge, both of which a tune-up is designed to catch before summer.
How it works
Airflow problems: filter, coil, and ducts
Cooling depends on a steady volume of air moving across a cold coil. A clogged filter, a dirty blower, or a frozen evaporator coil all starve that airflow, and ironically, restricted airflow is what causes the coil to freeze into a block of ice in the first place. If you see frost on the indoor coil or the copper lineset, the fix is to switch the system off, let it thaw, and replace the filter; if it ices again, the airflow or charge needs a technician.
Refrigerant: why 'just add more' is the wrong answer
An AC is a sealed system, so it doesn't 'use up' refrigerant the way a car uses gas. If the charge is low, there's a leak, and topping it off without finding and fixing the leak just buys a few weeks before you're back to warm air, while the compressor runs starved and overheats. A proper repair locates the leak, fixes it, and recharges to the manufacturer's spec. Low refrigerant often shows up as warm air, ice on the lineset, or a hissing sound.
Electrical: capacitors, contactors, and breakers
If the indoor fan runs but the outdoor unit is silent, the cause is often electrical, a failed run capacitor, a pitted contactor, or a tripped breaker. Capacitors and contactors are common, inexpensive parts that a technician can test and replace quickly. A breaker that keeps tripping, though, is a warning sign of a deeper electrical fault and shouldn't just be reset repeatedly, that's worth a diagnosis.
What to watch for
If you keep running a frozen system
Letting an iced-up AC keep running drives liquid refrigerant back to the compressor and can destroy the single most expensive part in the system. The moment you see frost on the coil or lineset, shut it off and let it thaw. A few hours off now is far cheaper than a compressor later.
If you keep resetting a tripping breaker
A breaker trips to protect you and the equipment. Repeatedly flipping it back on to squeeze out more cooling can damage the motor or wiring it's trying to protect, and in the worst case is a fire risk. A breaker that won't stay set needs a technician to find why, not another reset.
Why trust Burnside
- Burnside prioritizes no-cooling calls and gives you a clear appointment window.
- Every technician is licensed, insured, and background-checked, and explains the diagnosis in plain English.
- We quote flat-rate repair pricing before the work starts, you approve it before we begin.
Reviewed by the Burnside team, serving Collin County since 1958 · Last updated June 25, 2026
Common questions
Why is my AC running but not cooling? +
The most common causes are a clogged filter or frozen coil choking airflow, a low refrigerant charge from a leak, or an electrical part like a capacitor. Check the thermostat, breaker, and filter first; if those are fine, especially if you see ice or hear hissing, turn the system off and have it diagnosed before the compressor is damaged.
Should I just add refrigerant to my AC? +
No. An AC is sealed and doesn't consume refrigerant, so a low charge means a leak. Adding refrigerant without fixing the leak only masks the problem for a few weeks while the compressor runs starved. The right repair finds the leak, fixes it, and recharges to spec.
My outdoor unit is silent but the indoor fan runs, what's wrong? +
That pattern usually points to an electrical issue at the outdoor unit, often a failed capacitor or contactor, or a tripped breaker. These are common and repairable. If the breaker keeps tripping, stop resetting it and get it checked, that's a sign of a deeper fault.