Heat Pump Running But Not Heating: Troubleshooting Guide & Solutions For Homeowners

If a heat pump is running but not heating, it creates discomfort, increased energy bills, and uncertainty in American households. This guide details the most common reasons—ranging from thermostat errors to refrigerant leaks—and provides actionable solutions. Understanding troubleshooting steps and when to call a professional helps keep your home warm and your system efficient.

Possible Cause	Typical Symptoms	DIY Actions	When to Call a Technician
Thermostat Issues	System runs, no heat output	Check settings, replace batteries	If wiring or calibration issues found
Dirty Filters	Reduced airflow, lukewarm air	Replace or clean filters	If airflow remains weak after filter change
Frozen Outdoor Unit	Ice on coils, system struggles	Clear debris, check for obstructions	If frequent freezing occurs
Refrigerant Leaks	Hissing sounds, uneven heating	None; refrigerant handling requires certification	If low refrigerant suspected
Reversing Valve Failure	Stuck in cooling mode, no heating	None; component replacement needed	If switching modes is ineffective

How Heat Pumps Work And Why They May Stop Heating

A heat pump transfers heat from the outside air to inside your home, even on cold days. It uses a cycle of evaporation and condensation. If your heat pump is running but not heating, it indicates a breakdown in this process. Recognizing the core principles helps with troubleshooting and knowing when intervention is needed.

Key Operating Components

Compressor: Circulates refrigerant through the system.
Reversing Valve: Switches flow for heating or cooling.
Air Handler: Moves warmed or cooled air indoors.
Thermostat: Controls system operation and temperature settings.
Outdoor Unit: Contains the compressor, coil, and fan to facilitate heat transfer.

If any part fails or operates incorrectly, the system may run endlessly without producing adequate heat.

Setting And Calibrating The Thermostat Correctly

The thermostat acts as the system’s brain, directing when to activate heating. If misconfigured, the heat pump might operate in cooling mode or not heat at all. Start troubleshooting by reviewing all thermostat settings. Ensure the system is set to “heat” and the temperature setpoint is higher than room temperature.

Actions Homeowners Can Take

Check and replace thermostat batteries if needed.
Verify wiring connections if comfortable doing so (turn off breaker first).
Calibrate the thermostat or replace with a programmable model for more precise control.

Signs Of Thermostat-Related Issues

Display appears blank or flickers.
System does not respond to setting changes.
Heat pump fan runs, but no warm air is produced.

If these steps do not resolve the problem, a technician should inspect for console malfunctions or wiring defects.

Air Filter Problems And Airflow Restrictions

A clogged or dirty air filter inhibits airflow, making it difficult for warm air to reach living spaces. This is one of the most common causes when a heat pump is running but not heating effectively.

How To Check And Replace Filters

Locate the filter (in the air handler or return vent).
Remove and inspect: visible dust or discoloration means it’s time to change.
Install a replacement matching the original filter dimensions and type.

Replace filters every 1-3 months or as recommended for your region and system usage to maintain optimal airflow and heating efficiency.

Frozen Outdoor Unit: Causes And Remedies

During cold, wet, or icy weather, the outdoor coils may freeze over. Ice inhibits the transfer of heat, resulting in diminished heating. Modern heat pumps have a “defrost” cycle designed to address this, but malfunctions can prevent the cycle from operating.

What Homeowners Can Do

Visually inspect the outdoor unit after shutting off the system at the breaker.
Clear leaves, debris, or snow from around the unit for proper airflow.
Gently melt ice buildup using warm (not boiling) water—never use sharp tools.

If the problem recurs or the coils remain icy, the defrost control board or temperature sensors may be faulty. Professional assistance is necessary in these cases.

Refrigerant Issues And Leaks

Low refrigerant levels severely impair a heat pump’s ability to extract and move heat. Running a heat pump with insufficient refrigerant can cause compressor damage and increase repair costs. Refrigerant should be handled only by EPA-certified professionals.

Symptoms Of Refrigerant Problems

Constant operation with little to no warm air output.
Unusual hissing, bubbling, or gurgling sounds from the indoor or outdoor units.
Visible ice formation on the refrigerant lines or coils.

What To Do

Shut down the system and contact a licensed HVAC technician immediately.
Do not attempt DIY refills—there are legal and safety risks.

Reversing Valve Malfunctions

The reversing valve allows the heat pump to reverse the direction of refrigerant flow, switching between cooling and heating modes. If it fails, the heat pump might stay stuck in cooling mode even during heating calls.

Detecting Valve Failures

System will not switch from cool to heat or vice versa.
You may hear a rapid “click” or “hum” without temperature change.
The air coming from vents remains unheated, regardless of thermostat settings.

Solution

Contact an HVAC professional for reversing valve diagnostics and replacement.

Reversing valve replacement is a significant repair requiring specialized tools and experience.

Dirty Or Blocked Coils And Outdoor Fan Issues

Evaporator and condenser coils transfer heat between the air and the refrigerant; dirt or debris impedes this process. Likewise, a faulty outdoor fan or restricted fan intake restricts airflow, leaving your heat pump running but not heating the home properly.

How To Maintain Clean Coils And Fans

Shut off power to the system before any cleaning.
Use a soft brush or low-pressure hose to clear the outdoor unit’s coils of debris and dirt.
Remove yard debris, grass clippings, or mulch from the fan area.
Check that the fan spins freely and does not wobble.

If the fan motor fails to start or the blades are bent, professional service is required to avoid further system damage.

Electrical Problems And Control Board Failures

Modern heat pumps rely on circuit boards and relays to manage functions and safety checks. Failures in relays, fuses, or the control board may leave the compressor or heating cycle non-functional, even though the system runs.

Identifying Control Board Issues

Burning smells or visible scorch marks inside the air handler or outdoor unit.
Frequent tripping of circuit breakers or blown fuses.
System lights flashing error codes (check manufacturer’s manual for diagnostics).

Unless you are experienced with electronics and HVAC controls, these issues are best left to a certified technician for safe, reliable repairs.

Auxiliary Heating Problems In Dual Fuel And Cold Weather Systems

Many American heat pumps feature “auxiliary” or “emergency heat”—electric resistance coils that assist in extremely cold conditions. If these backup heaters malfunction, the main heat pump may run constantly without achieving set temperatures.

Signs Of Auxiliary Heat Failure

System indicates “aux” or “emergency” heat on the thermostat display but the home remains cold.
No noticeable increase in energy consumption when “aux” is enabled.
Unusual burning smells or tripped breakers when auxiliary heat activates.

Recommended Actions

Ensure no error indicators or warning lights are active on the thermostat or air handler.
Verify that auxiliary heat breakers or fuses are not tripped.
If issues persist, schedule service to inspect heating elements, limit switches, and safety controls.

Programmable And Smart Thermostats: Their Impact On Heat Pump Performance

Upgrading to a modern smart or programmable thermostat can significantly enhance heat pump heating performance and reduce power bills. These devices allow better scheduling, remote operation, and more responsive temperature control.

Tips For Optimal Settings

Program lower temperatures for overnight or work hours to minimize unnecessary operation.
Use gradual temperature increases to avoid excessive reliance on auxiliary heat in winter.
Ensure compatibility between your thermostat and heat pump model—especially if auxiliary or dual-fuel heating is present.

Improved temperature management can prevent unnecessary system cycling and significantly extend equipment life.

Energy Efficiency Considerations When Your Heat Pump Isn’t Heating

Heat pumps that run continuously but don’t heat are highly inefficient, wasting electricity and accelerating system wear. Diagnosing and addressing the specific cause is essential for restoring both comfort and cost control.

Energy Waste Indicators

Increased energy bills with no significant change in outdoor temperatures or household activity.
System runs for hours without reaching the thermostat setpoint.
Short cycling (turning on and off rapidly) or “hard starting.”

Timely maintenance, filter changes, and professional servicing are critical to sustaining both operational performance and long-term energy savings.

When To Call A Professional HVAC Technician

While many basic heat pump issues have DIY remedies, some problems pose safety risks or require specialized tools and certifications.

Situations Requiring Professional Assistance

Suspected refrigerant leaks or loss of charge.
Repeated freezing/defrost issues in the outdoor unit.
Electronics, wiring, or control board faults.
Continuously tripped breakers or electrical burning smells.
Reversing valve or compressor malfunctions.

Regular tune-ups (at least once a year) by qualified technicians can preempt many heating performance failures and protect warranty coverage.

Heat Pump Maintenance Tips To Prevent Heating Loss

Consistent maintenance is the frontline defense against most causes of heat pumps running but not heating. These steps extend equipment life and keep efficiency high.

Annual And Seasonal Checklist

Inspect and replace air filters monthly during peak usage.
Clear vegetation and debris at least 2 feet around the outdoor unit.
Schedule professional coil cleaning every 12-24 months.
Test thermostat performance and cooling/heating transitions before each season.
Monitor system sounds for changes that may indicate emerging faults.

Proactive upkeep is critical for reliable comfort and low operating costs year-round.

Upgrading Or Replacing An Aging Heat Pump System

If a heat pump is over 10-15 years old and frequently fails to heat, replacement may provide better reliability and energy savings compared to repeated repairs. Technological advances since 2015 mean newer models offer up to 30%-50% higher efficiency.

Factors To Consider When Replacing

Regional climate and heating/cooling load requirements.
Efficiency ratings (SEER, HSPF) and ENERGY STAR certification.
System sizing (tonnage) matched to home square footage and insulation.
Available rebates, tax credits, and financing options for eligible upgrades.

Consult a reputable HVAC contractor for a home assessment and customized system recommendations before making an investment.

Frequently Asked Questions About Heat Pumps Not Heating

Question	Brief Answer
Why does my heat pump run but blow cold air in winter?	Potential reasons include thermostat errors, low refrigerant, dirty filters, or reversing valve faults. Detailed troubleshooting is required.
How often should I replace my air filter?	Every 1-3 months, or as soon as it appears dirty. High-use households or allergy-prone areas may need more frequent changes.
Can I add refrigerant to my heat pump myself?	No; only licensed professionals legally handle refrigerant due to EPA regulations and safety hazards.
Does ice on my outdoor unit always indicate a problem?	Not always; temporary ice during a defrost cycle is normal, but persistent/frequent ice suggests a fault.
Is it worth repairing an old heat pump?	If repairs exceed half the cost of a new unit or the system is past its expected lifespan, replacing is often a better long-term value.

Key Takeaways For Efficient And Reliable Heat Pump Heating

Consistent performance and home comfort depend on recognizing early signs of trouble.
DIY troubleshooting should focus on simple actions like filter changes and settings checks.
Complicated faults—especially refrigerant, electrical, or component failures—require professional attention.
Seasonal maintenance and timely upgrades are the best strategies for reliable, economical heat pump operation.

Addressing the causes of a heat pump running but not heating will restore warmth, reduce bills, and protect your investment for years to come.