It’s the middle of summer in San Diego. Your AC is on, the fan is blowing—but your home still feels warm and stuffy. Sound familiar?
If your air conditioner is running but not cooling, you’re not alone. This is one of the most common complaints we hear from homeowners during peak heat. The good news? Many causes are easy to fix—especially if you catch them early.
Let’s break down the most common reasons your AC isn’t keeping up—and when it’s time to call in the pros.
1. Your Air Filter Is Dirty or Clogged
This is the #1 culprit we see.
A dirty air filter restricts airflow, making it harder for your AC to push cool air through your home. It also causes the system to work overtime, which can lead to bigger problems like frozen coils or overheating.
✅ Fix: Check and replace your air filter every 30–90 days, especially during the summer.
2. Your Thermostat Is Set Incorrectly
Sometimes the problem isn’t the AC—it’s the thermostat. A setting on “Fan” instead of “Cool,” or a miscalibrated thermostat, can blow room-temperature air even when the system is running.
✅ Fix: Make sure your thermostat is set to Cool and the fan is on Auto, not On. Replace the batteries if needed.
3. You Have a Refrigerant Leak or Low Refrigerant
Refrigerant is the chemical that cools the air inside your system. If levels are low—often due to a leak—your AC can’t effectively remove heat from your home.
⚠️ Warning: Refrigerant isn’t something you can refill yourself. It’s a pressurized chemical that requires EPA-certified handling.
✅ Fix: Call Blue Diamond for a refrigerant check and leak repair.
4. Your Evaporator Coil Is Frozen
A frozen coil can happen if airflow is restricted or there’s a refrigerant issue. You might notice ice buildup on the indoor unit or water leaks near the air handler.
✅ Fix: Turn off the system to let it thaw, check the filter, and call for service if the problem returns.
5. Your Outdoor Unit Is Dirty or Blocked
The condenser unit outside needs space and clean coils to release heat. If it’s clogged with leaves, dirt, or debris, it can’t do its job—and your home stays warm.
✅ Fix: Turn off power to the unit and gently rinse the coils with a hose. Keep at least 2 feet of clearance around the unit.
6. Your AC System Is Undersized or Aging
Older systems—especially those over 10–15 years old—may struggle to cool your home efficiently, especially during extreme heat. If your system runs constantly but still can’t keep up, it might be time for an upgrade.
✅ Fix: Schedule an AC assessment to see if your system is the right size and in good working order. Modern systems are quieter, more efficient, and often qualify for rebates.
When to DIY—and When to Call a Pro
| Issue | Try This First | Call a Pro If… |
|---|---|---|
| Weak airflow | Replace filter, check vents | Air still doesn’t flow properly |
| AC blowing warm air | Check thermostat settings | You’ve verified settings and it’s still warm |
| Ice on coils or water dripping | Turn off unit and thaw | Ice keeps returning or system won’t restart |
| Outdoor unit loud or not turning on | Clean debris, reset breaker | Unit is unresponsive or makes grinding sounds |
Don’t Sweat It—We’ll Fix It Fast
At Blue Diamond Heating & Air, we’ve helped hundreds of San Diego homeowners troubleshoot and fix their cooling problems quickly—before they turn into bigger, more expensive issues.
Schedule an AC Diagnostic →
We’ll inspect your system, fix the issue, and get your home back to cool comfort.
