Heat Pump Not Cooling: Causes, Troubleshooting, and Solutions

Heat pumps that stop cooling create discomfort and can signal underlying issues that affect performance and costs. This article explains the common reasons a heat pump is not cooling, step-by-step troubleshooting, repair and maintenance options, and guidance on when to hire a professional. The goal is to help homeowners identify problems quickly and make informed decisions.

Issue	Quick Check	Likely Fix
Thermostat Settings	Mode/Temperature	Reset/Reprogram
Dirty Air Filter	Restricted Airflow	Replace/Clean Filter
Refrigerant Leak	Ice On Coils/Low Pressure	Call HVAC Technician
Electrical Fault	Tripped Breaker/No Power	Reset/Repair Wiring

How Heat Pumps Cool: A Brief Overview

Heat pumps move heat from one place to another using refrigerant and a compressor instead of generating cold air. In cooling mode, the outdoor unit absorbs indoor heat and releases it outside while the indoor evaporator coil removes heat from return air. Proper airflow, refrigerant charge, compressor function, and control signals are essential for cooling.

Common Causes Why A Heat Pump Is Not Cooling

When a heat pump stops cooling, several mechanical, electrical, and user-related factors may be involved. Identifying the root cause narrows repair steps and prevents unnecessary expenses.

Thermostat Misconfiguration Or Failure

Incorrect thermostat settings, a dead battery, wrong mode (heat instead of cool), or a malfunctioning thermostat can prevent the heat pump from entering cooling mode. Calibration issues may cause the system to short-cycle or ignore temperature changes.

Restricted Airflow

Restricted airflow from clogged filters, blocked vents, closed dampers, or a dirty evaporator coil reduces cooling capacity. Poor airflow often leads to frozen coils and reduced refrigerant evaporation.

Refrigerant Problems

Low refrigerant charge from leaks or improper initial charging prevents the heat pump from absorbing enough heat. Signs include ice on the evaporator coil, hissing noises, and longer run times without temperature change.

Compressor Or Outdoor Unit Failures

The compressor is the heart of the refrigeration cycle; if it fails or the outdoor fan motor doesn’t run, the system cannot reject heat outdoors. Symptoms include loud or unusual noises, no cycling, or overheating protection tripping.

Electrical Issues

Tripped breakers, blown fuses, bad contactors, damaged wiring, or failed capacitors can disable the outdoor unit or prevent the compressor from starting. Intermittent power can cause erratic operation and increased wear.

Reversing Valve Or Control Board Faults

Heat pumps use a reversing valve to switch between heating and cooling. If the valve or control board fails, the unit might remain in heating mode or not engage the cooling sequence. Diagnostic lights or error codes often indicate control problems.

Undersized Or Malfunctioning Ductwork

Leaky, undersized, or poorly insulated ducts reduce delivered cooling and create temperature imbalances. Duct issues increase run times and energy bills while leaving rooms undercooled.

Step-By-Step Troubleshooting Checklist

This checklist helps homeowners perform safe, initial troubleshooting before calling a technician. If any step involves electrical components beyond comfort, contact a licensed HVAC technician.

1. Check Thermostat Settings: Ensure the thermostat is set to cool and the temperature is below room temperature. Replace batteries and verify program schedules.
2. Inspect Air Filter: Remove and examine the filter. Replace or clean if dirty. A clogged filter is a common, easy fix.
3. Examine Outdoor Unit: Verify the outdoor unit is running. Look for debris, vegetation, or ice buildup on the coils. Clear at least two feet of clearance around the unit.
4. Check Circuit Breakers: Inspect the home’s electrical panel and the outdoor disconnect for tripped breakers or blown fuses. Reset if safe and monitor for re-tripping.
5. Listen For Unusual Noises: Grinding, buzzing, or loud clicking can indicate motor or compressor issues. Document sounds and timing for the technician.
6. Inspect Indoor Evaporator Coil: If accessible, look for frost or ice. A frozen coil usually indicates airflow restriction or low refrigerant.
7. Look For Refrigerant Leaks: Oil stains or visible hissing near refrigerant lines can signal a leak. Refrigerant handling requires a certified technician.
8. Check for Error Codes: Some systems have diagnostic lights or thermostat error messages. Note codes for service techs.

DIY Fixes Homeowners Can Safely Try

Several issues can be resolved without professional help. These tasks are low risk and help restore normal cooling for many common problems.

• Replace Or Clean The Air Filter: Swap disposable filters or wash reusable ones monthly during heavy use.
• Clear Outdoor Unit Obstructions: Remove leaves, grass, and debris. Clean fins gently with a soft brush.
• Reset Breakers And Disconnects: Reset tripped breakers and the outdoor unit’s disconnect switch if safe to do so.
• Reboot The Thermostat: Turn the thermostat off, wait a minute, and power it back on. Recalibrate or update settings if needed.
• Ensure Vents And Registers Are Open: Close few unused registers to balance airflow, but avoid overpressurizing ducts.

When Professional Repair Is Required

Some problems require specialized skills, tools, and safety protocols that only licensed HVAC technicians should perform. Calling a professional is essential for refrigerant, electrical, compressor, and sealed-system repairs.

• Refrigerant Leaks And Recharge: Federal regulations require certified technicians to handle refrigerant. Leaks must be located and repaired before recharging.
• Compressor Replacement Or Major Component Failures: Replacing compressors, reversing valves, or indoor coil assemblies is complex and usually costly.
• Electrical Diagnostics And Motor Replacement: Capacitor replacement, contactor repair, or rewiring should be handled by a pro to avoid hazards.
• Control Board And Thermostat Integration Issues: Technicians can read error codes, update firmware, and test control sequences.

Preventative Maintenance To Keep A Heat Pump Cooling Efficiently

Regular maintenance extends equipment life, improves comfort, and reduces breakdowns. A proactive approach helps avoid summertime failures when cooling demand is highest.

• Schedule Professional Tune-Ups Twice Yearly: One visit for cooling-season preparation and one for heating-season checks.
• Replace Filters Every 1–3 Months: Use the manufacturer-recommended MERV rating for balance between filtration and airflow.
• Keep Outdoor Unit Clear: Maintain two feet of clearance, trim vegetation, and clean debris seasonally.
• Seal And Insulate Ductwork: Reduce leaks, improve airflow, and maintain balanced rooms.
• Check Refrigerant Pressure Annually: Technicians should verify charge and look for leaks during service.

Energy Efficiency And Cost Considerations

Inefficient cooling raises energy bills and reduces comfort. Addressing the root causes of cooling failure often lowers energy use and increases system longevity.

Heat pumps have high seasonal efficiency ratings (SEER and HSPF). Problems like low refrigerant, clogged coils, or compressor strain reduce efficiency dramatically. Replacing worn components, upgrading to a higher-efficiency model, or improving home insulation and ductwork can provide long-term savings.

Estimated Repair And Replacement Costs

Costs vary by region, system size, and problem severity. Below are general U.S. ranges to set expectations; actual quotes may differ.

Service	Typical Cost Range
Basic Tune-Up	$75–$200
Filter Replacement	$10–$60
Capacitor Or Contactor Replacement	$150–$450
Refrigerant Repair And Recharge	$200–$1,200+
Compressor Replacement	$1,200–$3,500+
Full Heat Pump Replacement	$4,000–$12,000+

Homeowners should request itemized estimates and consider system age, remaining useful life, and energy savings when deciding between repair and replacement.

Safety Tips And Regulatory Considerations

Handling refrigerant and high-voltage components can be hazardous. Federal and state rules regulate refrigerant handling and disposal. Only EPA-certified technicians should service refrigerant systems. Always disconnect power before inspecting components and avoid removing access panels on electrical equipment unless qualified.

Signs It May Be Time To Replace The Heat Pump

Replacement is often more economical when recurring repairs climb, efficiency drops, or the system is near the end of its typical 10–15 year lifespan. Consider replacement when the following occur: frequent compressor failures, major sealed-system repairs, mounting energy bills despite proper maintenance, or comfort problems that persist after repairs.

Questions To Ask A Service Technician

When contacting an HVAC professional, use clear questions to evaluate expertise and options.

• Is the technician licensed and insured, and are they EPA-certified for refrigerant handling?
• What diagnostic steps will be taken, and are diagnostic fees waived with repair?
• Can the technician provide a written estimate, parts warranty, and labor warranty?
• Are energy-efficient replacement options and expected payback discussed?

Frequently Asked Questions

Why Is My Heat Pump Running But Not Cooling?

Running without cooling usually indicates airflow problems, low refrigerant, compressor failure, or thermostat/control issues. Run the troubleshooting checklist to narrow the cause.

Can A Frozen Coil Damage The Heat Pump?

Yes. Operating with a frozen coil stresses the compressor and reduces lubrication. Thawing and fixing underlying causes—often airflow or refrigerant—should be done promptly.

How Long Should A Heat Pump Last?

With regular maintenance, a heat pump typically lasts 10–15 years. Higher-quality units and proactive servicing can extend lifespan beyond 15 years.

Is It Normal For A Heat Pump To Run Constantly In Hot Weather?

Longer run times can be normal during very hot weather, but continuous operation that fails to reach set temperature suggests a problem such as low refrigerant, clogged coil, or insufficient capacity.

Resources And Next Steps

If basic troubleshooting does not restore cooling, homeowners should gather system information—model, serial number, age, maintenance history, and observed symptoms—before calling an HVAC professional. Documenting what was checked and any error codes speeds diagnosis and helps ensure accurate estimates. For safety and legal compliance, refrigerant and major electrical work should always be performed by licensed technicians.

Addressing heat pump not cooling issues promptly preserves comfort, limits repair costs, and improves energy efficiency.