Why is my AC unit not cooling but running constantly?

An AC that runs nonstop without cooling often has a frozen evaporator coil or low refrigerant. Cleaning the coil and checking airflow helps.

Category:HVAC

Difficulty:Moderate

Time:45 min

Success:50%

Updated:Jun 19, 2026

quick_referenceQuick Answer

For Why is my AC unit not cooling but running constantly?, start with "Turn off the AC and check the filter": Set the thermostat to 'OFF' and switch the fan to 'ON'. Remove the air filter and hold it up to light. If it's dirty, replace it. Stop DIY if the outdoor unit is making a hissing or bubbling sound (refrigerant leak). This is listed as a moderate recovery and usually takes about 45 min.

verifiedGuide Snapshot

Repair areaHVAC

Estimated time45 min

DifficultyModerate

Stop conditions3

Last updated Jun 19, 2026. Review the stop conditions before continuing.

account_treeRecovery State

DeviceAc Unit

Current stateNot Cooling

Specific stateFrozen Coil

Failed stepEvaporator Coil Icing

Likely failure typeBlocked Path

DIY boundaryDIY recovery first

paymentsCost decision

help1. Understand the Problem

If your AC runs continuously but doesn't cool, the evaporator coil inside the air handler may be frozen. This usually happens due to restricted airflow (dirty filter) or low refrigerant levels. Ice on the coil prevents heat absorption, so the unit runs without reducing room temperature.

build_circle2. Try This First

Best First Step

Turn off the AC and check the filter

Set the thermostat to 'OFF' and switch the fan to 'ON'. Remove the air filter and hold it up to light. If it's dirty, replace it.

visibility3. Visual Guidance

See what's happening and how to try the first recovery step.

Inspect the evaporator coilOpen the air handler panel. Look for ice or frost on the coil. If frozen, leave the fan running for 2 hours to thaw it.

Clean the condenser unit outsideTurn off power to the outdoor unit. Remove debris from the fins using a soft brush. Rinse with a garden hose from inside out.

Check the condensate drainLocate the PVC drain line near the indoor unit. Pour a cup of vinegar or bleach down the vent to clear algae buildup.

autorenew4. If That Doesn't Work

Try the next recovery options.

Call an HVAC technician for refrigerant rechargeIf cleaning the filter and coil doesn't work, low refrigerant is likely. This requires a professional to find and fix the leak.

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