1. A dirty air filter
A clogged filter chokes airflow across the indoor coil. The system runs constantly, cools poorly and can eventually freeze up. This is the cheapest fix on the list. Replace the filter and give the system a few hours. See how often to change your filter.
2. A failed capacitor
The capacitor gives the outdoor compressor and fan motor the jolt they need to start. Heat is hard on capacitors, and they're one of the most common summer failures. A telltale sign: the indoor fan runs, but the outdoor unit hums or doesn't start. This is a quick repair for a licensed tech, but don't attempt it yourself. Capacitors store a charge.
3. A dirty condenser coil
The outdoor unit gets rid of the heat pulled from your home. When its coil is matted with pine pollen, cottonwood fluff, grass clippings or dirt, it can't shed heat and cooling drops off sharply. Kingwood's tree canopy makes this especially common. See pine pollen and your AC.
4. Low refrigerant from a leak
Refrigerant isn't used up. If it's low, it's leaking. Signs include ice on the copper lines, a hissing sound, or a system that cools a little but never reaches the set temperature. A technician needs to find and repair the leak, not just top it off.
5. An outdoor fan motor failure
If the outdoor unit is running but the fan on top isn't spinning, the compressor can overheat quickly. Turn the system off and call for service.
6. Thermostat problems
Dead batteries, a wrong mode setting, or a thermostat mounted in a sunny spot can all cause poor cooling. Check the basics before assuming a bigger problem.
7. Leaky or undersized ductwork
If some rooms are cool and others aren't, especially upstairs, the problem may be in the ducts rather than the equipment. Many older Kingwood homes still have original ductwork in very hot attics. See ductwork and airflow.
When to stop troubleshooting
If you've changed the filter, checked the thermostat and breaker, and the outdoor unit is clean but the house still isn't cooling, it's time for a licensed AC repair visit. Turn the system off in the meantime to protect the compressor.