Cooling help for Houston homeowners
AC Not Cooling in Houston? Likely Causes and Safe Checks
Learn why a Houston AC may stop cooling, which checks are safe for a homeowner, and when to turn the system off and call us.
Written by William Bonilla
Reviewed by Sotero Bonilla, TDLR License TACLB23855E
Last updated
What should I do when my AC stops cooling?
An air conditioner that runs without cooling may have a thermostat, airflow, outdoor-unit, refrigerant, or compressor fault. Check thermostat settings and accessible batteries, inspect the filter, keep vents clear, and observe the closed outdoor unit for fan movement, ice, or water. A technician must use electrical, airflow, and refrigeration measurements to confirm the cause.
When an AC runs without cooling, or does not start at all, the problem can be as simple as a thermostat setting or as involved as a refrigerant or compressor fault. In Houston heat, indoor temperatures can climb quickly. Check on older adults, children, and pets while you work through the safe steps below.
The clues that matter most are whether the thermostat is awake, whether air moves at the vents, whether the outdoor fan spins, and whether you see ice or water. These observations help narrow the cause without opening any equipment.
What causes an AC to stop cooling?
An AC may stop cooling because of a failed run capacitor, failed dual run capacitor, clogged condensate drain or tripped float switch, low refrigerant charge or a leak, or a frozen evaporator coil. Electrical, airflow, and refrigeration measurements identify which of these is actually at fault.
These are possibilities, not a diagnosis. The order starts with common explanations, but the right answer depends on the equipment and what it does during testing.
Failed run capacitor
A weak capacitor can leave the outdoor unit humming while its fan or compressor cannot start.
Failed dual run capacitor
One failed dual capacitor can stop both the outdoor fan and compressor or leave the unit humming.
Clogged condensate drain or tripped float switch
Algae can block the condensate drain, fill the pan, and trip a float switch that prevents overflow.
Low refrigerant charge or a leak
A refrigerant leak weakens heat transfer, lengthens cycles, and may create ice on visible lines.
Frozen evaporator coil
Low airflow or refrigerant trouble can freeze the indoor coil until little useful air reaches the rooms.
Burnt or stuck contactor
Heat or insects can damage this outdoor electrical switch, causing no start, chattering, or incorrect operation.
Dead or failing thermostat
Dead batteries or a failed thermostat can prevent the equipment from receiving a call to run.
Failed condenser fan motor
A worn outdoor fan motor may stay still while the compressor hums, causing overheating and poor performance.
Tripped breaker or blown disconnect fuse
A surge or overload can interrupt power, but a repeat trip signals a fault that needs testing.
Weak or failing compressor
A worn compressor may cool poorly, struggle to start, run constantly, or trip its breaker.
Leaking evaporator coil
An indoor coil leak lowers refrigerant charge, weakens cooling, and may create ice.
Failed low-voltage transformer
A failed low-voltage transformer can blank the thermostat and stop controls even when main power remains.
Failed AC control board
A failed cooling control board may stop the system or make its cycle behave erratically.
System at the end of its service life
Older equipment with repeated failures, high energy use, or a major fault may warrant comparing repair and replacement.
Failed metering device or TXV
A stuck metering device can weaken cooling and create uneven ice by feeding refrigerant incorrectly.
Stuck heat pump reversing valve
A stuck reversing valve may make a heat pump deliver the opposite of the thermostat request.
What is safe to check yourself
- Set the thermostat to COOL and choose a target below the room temperature. Confirm it is not on OFF or FAN ONLY. If the screen is blank and the thermostat uses accessible batteries, install fresh ones.
- Check an accessible air filter. If it is packed with dust and you cannot see light through it, replace it with the correct size. Make sure supply vents and the large return grille are open and clear.
- From outside, look and listen without opening the unit or reaching through its grille. Note whether the fan is spinning, the unit is silent, or it only hums. Also look for ice on visible refrigerant lines.
- Look around the indoor unit for standing water and check whether an accessible drain float switch appears raised. Observe only. Do not remove panels or touch wiring.
Keep every equipment panel closed. Do not touch wiring, pull an outdoor disconnect, or handle any internal part.
Stop and call right away if...
- If you see smoke or sparks, get everyone outside and call 911. Do not open the equipment or try to find the source.
- If water is touching wiring, an outlet, or electrical parts, do not touch the unit or the water. Shut off power only if you can reach the breaker safely, then call for service.
- If you smell burning or hot electrical parts, turn the system off at the thermostat. Shut off its breaker only if safe. Leave and call 911 if there is smoke or sparking.
What a technician will actually do
A technician will confirm the thermostat call, measure electrical components, inspect airflow, and check the refrigeration cycle. The order of testing follows the clues you observed, so a stopped fan, ice, water, or a blank thermostat all matter.
The goal is to identify the failed part or condition before discussing repair. The technician may also compare repair and replacement only when equipment condition and age make that useful.
Questions homeowners ask
- Why is my AC running but not cooling the house?
- Common causes include a dirty filter, frozen coil, dirty outdoor coil, low refrigerant, a failed fan component, or a weak compressor.
- Can I keep running an AC that is not cooling?
- Turn cooling off if you see ice, hear a loud mechanical sound, smell burning, or the breaker trips again. Continued operation can worsen the fault.
- What can I safely check before calling for AC repair?
- Check thermostat settings and batteries, the filter, open vents, the outdoor unit from outside, visible ice, and standing water near the indoor unit.
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