Heat Pump Not Heating (Troubleshooting Guide)

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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, ensure the power is on, and verify the air filter is clean. If the issue persists, inspect the emergency heat setting and outdoor unit for obstructions.

Confirm the symptom

Indoor temperature is not rising
Heat pump is running but not producing warm air
Thermostat shows no heating activity

Tools and prep

Thermostat manual
Screwdriver set
Vacuum cleaner
Safety gloves
Flashlight
Ladder (if needed for outdoor unit)

Step-by-step troubleshooting

Check Thermostat Settings
Do: Verify the thermostat is set to 'Heat' mode and the desired temperature is higher than the current room temperature.
Observe: Thermostat displays correct settings and responds to changes.
Means: Thermostat is functioning correctly.
Next: If settings are correct, proceed to the next step.
Inspect Power Supply
Do: Ensure the heat pump's circuit breaker is on and the outdoor unit's power switch is in the 'On' position.
Observe: Power is restored to both indoor and outdoor units.
Means: Power supply is not the issue.
Next: If power is on, continue troubleshooting.
Check Air Filter
Do: Remove and inspect the air filter for dirt or blockage.
Observe: Air filter is clean or needs replacement.
Means: A dirty filter may restrict airflow and reduce heating efficiency.
Next: Replace the filter if necessary and test the heat pump again.
Verify Emergency Heat
Do: Check if the thermostat is set to 'Emergency Heat' mode and adjust it to 'Heat' if needed.
Observe: Thermostat switches to normal heating mode.
Means: Emergency heat mode was engaged, which may limit normal operation.
Next: Wait a few minutes to see if heating resumes.
Inspect Outdoor Unit
Do: Use a ladder to safely check the outdoor unit for ice buildup, debris, or obstructions.
Observe: Outdoor unit is clear of obstructions and free of ice.
Means: No physical blockage is preventing proper operation.
Next: If the unit is clear, proceed to the next step.
Test Auxiliary Heat
Do: Increase the temperature setting on the thermostat to activate auxiliary heat and observe if the system responds.
Observe: Auxiliary heat engages and the system starts heating.
Means: The auxiliary heat function is working correctly.
Next: If auxiliary heat does not engage, consider professional assistance.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Incorrect Thermostat Settings The thermostat is not set to 'Heat' or the temperature is not set high enough.	Common	Easy	None
Power Supply Issues The heat pump's circuit breaker is tripped or the outdoor unit's power switch is off.	Common	Easy	None
Dirty Air Filter A clogged air filter restricts airflow, reducing heating efficiency.	Common	Easy	Air Filter
Emergency Heat Mode Activated The thermostat is set to 'Emergency Heat', which may limit normal heating operation.	Sometimes	Easy	None
Outdoor Unit Obstruction Debris, ice, or snow blocks the outdoor unit, preventing proper heat exchange.	Sometimes	Easy–Medium	None
Refrigerant Leak Low refrigerant levels prevent the heat pump from transferring heat effectively.	Sometimes	Hard	Refrigerant (Professional Service)
Faulty Defrost Timer The defrost timer fails to initiate the defrost cycle, causing ice buildup on the outdoor unit.	Rare	Hard	Defrost Timer (Professional Service)
Thermostat Malfunction A faulty thermostat may not send the correct signals to the heat pump.	Rare	Medium	Thermostat
Compressor Issues A malfunctioning compressor cannot circulate refrigerant, preventing heat production.	Rare	Hard	Compressor (Professional Service)
Electrical Problems Loose or damaged electrical connections disrupt the heat pump's operation.	Rare	Hard	Electrical Components (Professional Service)

Parts matching

Common parts needed for a heat pump not heating issue include:

Air Filter
Thermostat
Refrigerant (Professional Service)
Defrost Timer (Professional Service)
Compressor (Professional Service)

Always replace parts with manufacturer-recommended equivalents and consider professional installation for complex components.

When to call a professional

The heat pump still does not heat after checking all settings and components.
You notice a refrigerant leak or smell chemical odors.
The outdoor unit is heavily iced and defrost cycles are not working.
The system makes unusual noises or emits burning smells.
Error codes appear on the thermostat that you cannot resolve.
The problem persists for more than a day after troubleshooting.

FAQ

Can a dirty air filter cause my heat pump to stop heating?

Yes, a clogged air filter restricts airflow, reducing heating efficiency and potentially causing the system to overheat or malfunction.

What is emergency heat mode, and when should I use it?

Emergency heat mode uses electric resistance heating as a backup. Use it only if the heat pump fails to provide heat during extreme cold.

Why is my heat pump running but not blowing warm air?

This could be due to incorrect thermostat settings, a refrigerant leak, or a malfunctioning compressor. Check settings first, then consider professional help.

How often should I replace my air filter?

Replace the air filter every 1–3 months, depending on usage and environmental factors, to maintain optimal airflow and efficiency.

Can I fix a refrigerant leak myself?

No, refrigerant leaks require professional repair due to environmental regulations and the need for specialized equipment.

What should I do if my outdoor unit is iced over?

Turn off the power to the unit and allow the ice to melt naturally. Avoid using sharp objects to remove ice, as this can damage the unit.