Heat Pump Not Cooling

If your heat pump is not cooling, first check thermostat mode, filter condition, airflow, power, and whether the outdoor unit is operating.

A heat pump cools using the same basic refrigeration process as a central air conditioner, so many no-cooling causes overlap with AC problems.

For the broader repair decision, see the heat-pump repair guide.

Safety: Stop troubleshooting for repeated breaker trips, burning smells, exposed or damaged wiring, or suspected refrigerant leakage. If it is safe to use the thermostat, switch the system Off and call a qualified technician. For smoke or fire, move away from the equipment and contact emergency services.

Sources: Carrier heat pump troubleshooting, Carrier emergency guidance

1. Confirm the Thermostat Is in Cool Mode

Check:

• mode is Cool
• setpoint is below room temperature
• schedule has not changed the setting
• fan is not set in a way that confuses diagnosis
• thermostat batteries are good if used

Wait several minutes after mode changes.

2. Inspect the Filter

A severely clogged filter can reduce airflow across the indoor coil.

Replace a dirty filter with the correct type/size.

Poor airflow can contribute to:

• weak cooling
• coil icing
• longer runtime
• comfort problems

3. Check Registers and Returns

Open supply registers.

Make sure return grilles are not blocked.

If airflow is weak everywhere, the problem may involve the blower, filter, coil, or duct system.

4. Check Breakers Once

Verify relevant HVAC breakers.

One reset may be appropriate only if you know which circuit it serves and there is no burning smell, smoke, damaged wiring, or water near electrical equipment. Otherwise, leave it alone and call a professional.

If a breaker trips again after one reset, stop.

Do not repeatedly reset a circuit.

5. Check the Outdoor Unit

During a normal cooling call, the outdoor unit should generally be active unless the system/control design is in a special mode.

Look for obvious issues without opening the cabinet:

• heavy debris
• blocked airflow
• fan not running
• unusual noise
• visible damage

Do not reach through the grille or work inside energized equipment.

6. Is the Indoor Coil Frozen?

Possible clues:

• weak airflow
• reduced cooling
• visible ice on accessible refrigerant tubing/coil area
• water after ice melts

Possible causes include:

• restricted airflow
• dirty filter
• blower problem
• refrigerant issue
• control problem

Turn the system off if significant icing is present and arrange diagnosis.

Do not keep forcing it to cool through a frozen coil.

Common Causes of No Cooling

Potential causes include:

• thermostat/control problem
• dirty filter
• blocked airflow
• indoor blower problem
• outdoor fan problem
• dirty/blocked coil
• refrigerant leak
• compressor problem
• reversing-valve problem
• electrical fault
• duct leakage

A symptom does not identify the failed part by itself.

Why Is the Heat Pump Running but the House Is Still Hot?

Check whether the system is:

• producing cool supply air
• moving enough air
• keeping up during peak weather
• cycling normally
• using correct mode/settings

If the system cools but cannot maintain temperature, possible causes include:

• undersizing
• equipment fault
• duct leakage
• high building load
• dirty coils/filter
• extreme weather
• poor envelope

Heat pump sizing

Does a Reversing Valve Cause No Cooling?

It can.

The reversing valve changes refrigerant flow between heating and cooling modes.

But do not jump to that diagnosis from symptoms alone.

Other electrical, control, compressor, and refrigerant problems can look similar.

How Much Can Repair Cost?

Current Angi 2026 data places many common heat-pump repairs around $161-$661, with larger sealed-system repairs potentially much higher.

Source: Angi - Heat Pump Repair Cost, May 2, 2026

Heat pump repair cost

When Should You Consider Replacement?

Get a replacement quote when:

• equipment is older
• compressor/sealed-system repair is expensive
• failures repeat
• heating performance is also poor
• efficiency is weak
• other major upgrades are needed

Review repair-versus-replacement considerations.

Find Heat Pump Cooling Repair Near You

Get a qualified technician to diagnose the actual fault before approving a major part replacement. Use the heat-pump installer guide to evaluate providers.