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Why is my AC running but not cooling?

A running AC that doesn't cool usually means the system is operating but not transferring heat. The most common causes are listed here.

Before anything — check these

If any of these are true, stop and get professional help now:

Frozen lines and coil
Sizzling or grinding noises
Tripping breaker

Safe checks you can do

Tick what you've checked. Only do homeowner-safe actions.

Check for a frozen indoor coil (ice buildup).
Inspect outdoor condenser for dirt or obstruction.
Verify the fan is spinning on the outdoor unit.

Likely causes

Cause	Likelihood	Severity	Cost
Low refrigerant charge	high	Medium	$200–$1,500
Frozen evaporator coil	medium	Medium	$150–$600
Dirty condenser coils	medium	Low	$100–$300
Bad capacitor	medium	Medium	$150–$400

Recommended next action

Turn the system off if you see ice and let it thaw. If it keeps running without cooling, schedule a technician — the most likely culprit is refrigerant or a capacitor.

Related tools

AC Not Cooling — What To Check

Your AC is running but the house isn't getting cooler. The cause is usually simple — and often fixable before you call a pro.

AC Repair Cost (2026)

Most AC repairs are well under a quarter of a replacement. Here's what common repairs typically cost.

Plan the fix

Once you know roughly what's wrong, size the job and get a cost range:

HVAC System Planner