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AC Not Cooling: Troubleshooting Before You Call a Pro
Quick answer
- Run five safe checks first — thermostat, air filter, breaker (one reset), outdoor unit, and vents. They fix a large share of “not cooling” cases for $0–$30.
- If those are clear, it’s usually low refrigerant, a frozen coil, a dirty condenser coil, or a failed capacitor/compressor — licensed-pro repairs from about $120 to $2,800.
- Reset a tripped breaker only once. If it trips again, stop and call a pro.
- Hot house and you want it handled today? Get matched with a licensed local pro. — free, no obligation.
If your AC is running but the house isn’t getting cold, don’t pay for a service call yet. Five safe, cheap checks solve a surprising share of “not cooling” complaints in minutes. Work through them in order — each one rules out a common cause before you spend a dollar.
5 safe checks, in order
- Thermostat. Set mode to COOL (not heat or fan), the temperature a few degrees below the room, and the fan to AUTO. Replace the batteries — a $5 fix that often looks like a dead system.
- Air filter. A clogged filter is the #1 preventable AC problem. If you can’t see light through it, replace it ($15–$30). Restricted airflow can even freeze the coil.
- Breaker — one reset. Flip the AC breaker fully OFF, then back ON, once. If it trips again, stop — repeated tripping means an electrical fault a pro must diagnose.
- Outdoor unit. Is the fan spinning? Is the condenser smothered in leaves or cottonwood fluff? Clear two feet on all sides. A silent outdoor fan while the indoor unit runs points to a capacitor or contactor — a pro fix.
- Supply & return vents. Confirm every register is open and unblocked by furniture. Closing vents to “save energy” actually hurts cooling.
If all five are correct and the house still won’t cool, you’ve done the safe diagnostics. The remaining causes need a technician.
Ran the checks and still hot?
That points to refrigerant or an electrical fault — not a DIY job. Reach a licensed local pro now, free and no obligation.
Still not cooling? What’s probably wrong (and who fixes it)
| Likely cause | Who fixes it | Typical 2026 cost |
|---|---|---|
| Low refrigerant / leak | Licensed pro | $250–$1,600 (avg ~$800) |
| Frozen evaporator coil | You thaw + pro root-cause | $0 → $600+ |
| Failed run capacitor | Licensed pro | $120–$400 |
| Failed contactor / relay | Licensed pro | $100–$450 |
| Dirty condenser coil | Pro (or careful rinse) | $75–$250 |
| Bad compressor | Licensed pro (often replace) | $850–$2,800+ |
Low refrigerant only happens because of a leak. The fix is to find and seal the leak, then recharge — work that legally requires an EPA-certified technician. Skip “DIY recharge kits”; they don’t fix the leak and can damage the system. Refrigerant repair has gotten pricier as R-410A is phased down under the EPA AIM Act.
A failed capacitor ($120–$400) is a common, affordable culprit when the outdoor fan or compressor won’t start. A failed compressor ($850–$2,800+) is the expensive one — and on an older unit it often tips the decision toward replacement. Either way, the cabinet stores a dangerous charge even when powered off. Don’t open it.
When “not cooling” means replace, not repair
If your system is 12–15+ years old and the diagnosis is a failed compressor or a major refrigerant leak, the repair can approach half the price of a new system. The industry’s 50% rule: when a repair costs more than half of replacement, replace it. A unit still running R-22 refrigerant is an even stronger push toward replacement.