AC Not Cooling? Troubleshooting Guide for Texas Homeowners

Likely causes: Refrigerant leak, Frozen coil, Compressor failing

First check: Check for ice on refrigerant line and clean filter

Likely causes: Tripped breaker, Bad capacitor, Faulty contactor

First check: Reset both breakers, check thermostat batteries

Likely causes: Tripped breaker, Failed capacitor, Bad contactor

First check: Listen for humming at outdoor unit, check breaker

Likely causes: Blown motor, Bad capacitor, Faulty blower relay

First check: Check filter (clogged filter overheats motor)

Likely causes: Overheating, Refrigerant issue, Oversized system

First check: Check outdoor unit for debris blocking airflow

Likely causes: Dirty filter, Duct leak, Blower issue

First check: Replace filter, check for disconnected ducts

Likely causes: Duct problems, Damper settings, Undersized system

First check: Open all vents, check for duct damage in problem areas

The most common causes are: dirty air filter (restricting airflow and causing coil freeze), low refrigerant from a leak, dirty condenser coils outdoors, or a failing compressor. Start by replacing your air filter and checking if there's ice on the copper refrigerant line going into your house. If the filter is clean and there's no ice, you likely need professional diagnosis for a refrigerant or compressor issue.

A frozen evaporator coil typically takes 2-4 hours to fully thaw with the fan running (set to ON, not AUTO). Heavy ice buildup may take up to 24 hours. Never try to chip ice off—this damages the delicate coil fins. Place towels around the indoor unit to catch melt water and replace your air filter during the thaw process.

A properly functioning AC should produce supply air that's 15-20°F cooler than the room temperature. For example, if your room is 78°F, supply air should be 58-63°F. Anything less than a 10°F difference indicates a problem. Note that on extremely hot days (100°F+), this differential may be slightly lower due to system stress.

This is normal in Texas summers. As outdoor temperatures rise above 95°F (especially 100°F+), your AC's capacity decreases while your home's heat gain increases. Afternoon sun through west-facing windows adds tremendous heat load. Your AC may only be able to maintain 20-25°F below outdoor temperature on extreme days. Close blinds on west windows from 3-7 PM for better afternoon performance.

Signs of low refrigerant include: ice forming on the refrigerant line or indoor coil, gradual decline in cooling over weeks/months, hissing or bubbling sounds, higher energy bills, and longer run times. Only an EPA-certified technician can legally add refrigerant. Low refrigerant always indicates a leak that should be repaired—simply adding refrigerant without fixing the leak is a temporary and expensive band-aid.

It's fine to run your AC in extreme heat—that's exactly what it's designed for. However, expect it to run continuously and possibly struggle to reach your setpoint. Don't set your thermostat below 72°F hoping it will cool faster; it won't. Instead, set a realistic temperature (76-78°F), close blinds, avoid using the oven, and limit opening doors. Running ceiling fans allows you to feel comfortable at a higher thermostat setting.

After a power outage, check your thermostat settings first—some thermostats reset to default modes. Next, verify both circuit breakers (indoor and outdoor unit) aren't tripped. If the outdoor unit doesn't start within 5 minutes, the compressor may have thermal overload protection engaged and needs 30 minutes to reset. If warm air continues after these checks, a power surge may have damaged the capacitor or contactor.

Signs of a failed capacitor include: outdoor unit humming but fan not spinning, clicking sounds when trying to start, the fan spinning slowly at startup or needing a "push" to get going, or the system frequently tripping the breaker. Capacitors are common failure points in Texas due to extreme heat. Never attempt to test or replace a capacitor yourself—they hold a dangerous electrical charge even when power is off.

It depends on the symptom. If you see ice on the refrigerant line or hear unusual noises (grinding, screeching), turn it off immediately to prevent further damage. For other issues like weak cooling, you can leave it running while waiting for service—just don't expect it to keep up on hot days. If someone vulnerable is in the home and the AC isn't providing adequate cooling, consider alternative cooling arrangements rather than relying on a malfunctioning system.

If your AC freezes repeatedly despite a clean filter, the likely causes are: low refrigerant from a leak, blocked return vents, collapsed or disconnected ductwork, failing blower motor, or a dirty evaporator coil. A technician needs to check refrigerant levels and inspect the evaporator coil. Chronic freezing with a clean filter almost always indicates a refrigerant leak that's getting progressively worse.

"Not cooling" means no cold air from vents at all—this indicates a system malfunction requiring repair. "Not keeping up" means the AC produces cool air but can't maintain the desired temperature, especially on hot days. Not keeping up can be normal on 100°F+ days (expect indoor temps of 78-80°F), but if it's struggling on moderate days (under 95°F), you may have insufficient capacity, duct leaks, or home insulation issues.

Costs vary widely by cause: air filter replacement ($5-25 DIY), capacitor replacement ($150-350), refrigerant recharge with leak repair ($200-600), contactor replacement ($150-300), evaporator coil cleaning ($200-400), compressor replacement ($1,500-3,000+), or new system ($6,000-15,000). Diagnostic visits in North Texas typically run $89-150, often credited toward repairs. Age of system heavily influences repair vs. replace decisions—systems over 12 years old may not warrant major repairs.