Heat Pump Not Heating House: Troubleshooting Guide (Troubleshooting Guide)

On this page

Quick answer
Confirm the symptom
Tools and prep
Step-by-step troubleshooting
Common causes table
Parts matching
When to call a pro
FAQ
Related guides

Quick answer

Check the thermostat settings and power supply first. If the heat pump still doesn't heat, inspect the air filter and outdoor unit for obstructions. If issues persist, contact a professional HVAC technician.

Confirm the symptom

Indoor temperature is not rising despite the heat pump running
Heat pump fan runs but no warm air is produced
Thermostat shows heat call but no heating action
Outdoor unit is not operating when heating is needed

Tools and prep

Thermostat screwdriver
Flashlight
Vacuum cleaner with brush attachment
Multimeter (for voltage checks)
Safety gloves and goggles
Owner's manual for the heat pump

Step-by-step troubleshooting

Check Thermostat Settings
Do: Ensure the thermostat is set to 'Heat' mode and the desired temperature is higher than the current room temperature.
Observe: Thermostat displays correct mode and temperature.
Means: Thermostat is functioning correctly.
Next: If thermostat is set correctly, proceed to step 2.
Verify Power Supply
Do: Check the circuit breaker or fuse box to ensure the heat pump's power is on. Look for any tripped breakers or blown fuses.
Observe: Breaker is in 'on' position and no signs of tripping.
Means: Power supply is stable.
Next: If power is on, continue to step 3.
Inspect Air Filter
Do: Remove and examine the air filter for dirt or blockage. Clean or replace it if necessary.
Observe: Air filter is clean and allows unrestricted airflow.
Means: Airflow obstruction is resolved.
Next: If filter is clean, move to step 4.
Check Outdoor Unit
Do: Approach the outdoor unit and ensure it is free from snow, ice, or debris. Listen for any unusual noises or signs of operation.
Observe: Outdoor unit is clear and appears to be running without issues.
Means: Outdoor unit is accessible and operational.
Next: If unit is clear, proceed to step 5.
Test Emergency Heat
Do: If your system has emergency heat, switch it on via the thermostat. Observe if the system provides heat.
Observe: System delivers heat when emergency heat is activated.
Means: Auxiliary heat source is functional.
Next: If emergency heat works, consult a technician for further evaluation. If not, continue to step 6.
Check for Error Codes
Do: Look at the thermostat or heat pump control panel for any error codes or blinking lights. Refer to the owner's manual for code explanations.
Observe: No error codes or blinking lights are present.
Means: No immediate system faults detected.
Next: If no codes are found, proceed to step 7.
Measure Voltage
Do: Using a multimeter, test the voltage at the outdoor unit's disconnect box. Ensure it matches the system's requirements.
Observe: Voltage readings match the system's specifications.
Means: Electrical supply to the unit is correct.
Next: If voltage is correct, continue to step 8.
Inspect Refrigerant Levels
Do: Check for visible refrigerant leaks around the outdoor and indoor units. Look for oily residue or hissing sounds.
Observe: No signs of refrigerant leaks or low levels.
Means: Refrigerant system is intact.
Next: If no leaks are found, contact a professional HVAC technician for further diagnosis.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Thermostat Misconfiguration Incorrect settings can prevent the heat pump from activating the heating cycle.	Common	Easy	None
Clogged Air Filter A dirty filter restricts airflow, reducing heating efficiency and causing the system to work harder.	Common	Easy	Air Filter
Outdoor Unit Obstruction Snow, ice, or debris can block airflow to the outdoor unit, preventing proper heat exchange.	Common	Easy–Medium	None
Low Refrigerant Levels Leaking or insufficient refrigerant reduces the system's ability to transfer heat effectively.	Sometimes	Hard	Refrigerant (needs professional refill)
Faulty Defrost Cycle A malfunctioning defrost cycle can cause the outdoor unit to ice over, impairing its heating performance.	Sometimes	Medium	Defrost Control Board
Electrical Issues Tripped breakers, blown fuses, or wiring problems can cut power to the heat pump components.	Sometimes	Medium	Circuit Breaker/Fuse
Compressor Failure A failed compressor cannot circulate refrigerant, preventing the system from producing heat.	Rare	Hard	Compressor Unit
Thermostat Malfunction A faulty thermostat may not send the correct signals to activate the heating system.	Sometimes	Medium	Thermostat
Auxiliary Heat Failure If emergency heat is not working, the system may not provide sufficient heating during extreme temperatures.	Sometimes	Medium	Auxiliary Heat Strip
Reversing Valve Issue A stuck or faulty reversing valve prevents the system from switching to heating mode.	Rare	Hard	Reversing Valve

Parts matching

Common parts needed for heat pump heating issues include:

Air Filter – Replace if dirty or clogged
Thermostat – Test or replace if malfunctioning
Circuit Breaker/Fuse – Reset or replace if tripped/blown
Defrost Control Board – Replace if the outdoor unit is icing over
Auxiliary Heat Strip – Replace if emergency heat is not functioning
Refrigerant – Requires professional refill for leaks or low levels
Compressor Unit – Replace if the system is not circulating refrigerant

Always refer to your heat pump's owner's manual for part specifications and installation instructions.

When to call a professional

If the heat pump still doesn't heat after checking all basic issues
If you detect refrigerant leaks or smell a chemical odor
If the system produces unusual noises or vibrations
If error codes persist or recur after troubleshooting
If the outdoor unit is frozen or iced over and defrost cycle is not working
If the compressor does not engage or appears to be seized
If you're unsure about electrical checks or refrigerant handling

FAQ

How often should I replace my heat pump's air filter?

Replace the air filter every 1–3 months, depending on usage and indoor air quality. A dirty filter can reduce heating efficiency and strain the system.

Can I use my heat pump in very cold weather?

Heat pumps are less efficient in extreme cold (below 25–30°F). Consider using a dual-fuel system with a gas furnace for better performance in freezing temperatures.

Why is my heat pump making a loud humming noise?

A loud humming noise may indicate electrical issues, such as a failing capacitor or loose wiring. Turn off the system and contact a professional technician for inspection.

What is the average lifespan of a heat pump?

A well-maintained heat pump typically lasts 10–15 years. Regular maintenance and prompt repairs can extend its lifespan and efficiency.

How much does it cost to repair a heat pump that's not heating?

Repair costs vary depending on the issue. Minor fixes like replacing a filter or thermostat may cost $50–$200, while major repairs like compressor replacement can range from $1,000 to $3,000.