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Why is my AC unit not cooling the house?

An AC that runs but doesn't cool may have a dirty filter, frozen coils, or low refrigerant. Check here.

Category:HVAC

Difficulty:Easy

Time:20 min

Success:50%

Updated:Jun 10, 2026

quick_referenceQuick Answer

For Why is my AC unit not cooling the house?, start with "Replace the air filter": Turn off the system. Locate the filter slot near the indoor unit. Remove the old filter and insert a new one with the arrow pointing toward the blower. Stop DIY if you see ice on the refrigerant lines outside. This is listed as a easy recovery and usually takes about 20 min.

verifiedGuide Snapshot

Repair areaHVAC

Estimated time20 min

DifficultyEasy

Stop conditions3

Last updated Jun 10, 2026. Review the stop conditions before continuing.

account_treeRecovery State

Current stateInsufficient Cooling

Specific stateRuns But No Cold Air

Failed stepDirty Filter

Likely failure typeBlocked Path

DIY boundaryDIY recovery first

paymentsCost decision

help1. Understand the Problem

When your air conditioner runs but fails to cool, the most common causes are a clogged air filter, dirty condenser coils, or a refrigerant leak. Frozen evaporator coils can also block airflow. Start with simple checks before calling a pro.

build_circle2. Try This First

Best First Step

Replace the air filter

Replace the air filter

Turn off the system. Locate the filter slot near the indoor unit. Remove the old filter and insert a new one with the arrow pointing toward the blower.

visibility3. Visual Guidance

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

1

Step 1: Check the thermostat settings

Check the thermostat settingsEnsure the thermostat is set to 'Cool' and the temperature is below room temp. Replace batteries if needed.

2

Step 2: Inspect the outdoor unit

Inspect the outdoor unitMake sure the outdoor condenser unit is free of leaves, grass, and debris. Trim vegetation 2 feet around it.

3

Step 3: Check for frozen coils

Check for frozen coilsOpen the indoor air handler panel. If the evaporator coils are iced over, turn off the AC and run the fan only to thaw.

4

Step 4: Clean the condensate drain

Clean the condensate drainLocate the drain line near the indoor unit. Use a wet/dry vac or a pipe cleaner to clear clogs.

autorenew4. If That Doesn't Work

Try the next recovery options.

Clean the condenser coilsTurn off power, remove debris from outside unit, and spray coils with a garden hose.

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Frequently Asked Questions

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warning5. Stop DIY If

Don't continue if any of these apply.

reportYou see ice on the refrigerant lines outside

reportThe outdoor unit makes a loud buzzing or grinding noise

reportYou suspect a refrigerant leak (requires EPA certification to handle)

Still stuck?Get personalized help with AI Recovery.

Same Device Recovery States

Device index arrow_forward

AC Warm Air FixIf your air conditioner blows warm air, a dirty condenser coil, low refrigerant, or a faulty capacitor is likely the cause. Diagnose step by step.

AC not coolingIf your AC runs constantly but the house stays warm, the most likely cause is a frozen evaporator coil or a dirty condenser.

AC Not CoolingAn AC that runs but blows warm air can be due to a dirty condenser coil, low refrigerant, or a frozen evaporator. Here's how to troubleshoot.

AC Coil CleaningBoost your AC's cooling power by cleaning dirty condenser coils. No tools needed—just a hose and a few minutes.

AC Blowing Warm Air After Filter ChangeWarm air after a filter change often means the filter is installed backwards, the condenser unit is dirty, or the thermostat is set wrong.

AC Leaking Water InsideAn indoor AC unit leaking water usually means a clogged condensate drain line or a frozen evaporator coil. Clearing the blockage stops the leak.

Similar Failure Pattern

Slow kitchen sink drain Dryer not drying AC Warm Air Fix AC not cooling

This page provides general DIY guidance.
If you're unsure, it's always best to consult a professional.