Heat Pump Not Heating Troubleshooting (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, ensure the power is on, and inspect for tripped circuit breakers. If the issue persists, the air filter or refrigerant levels might need attention.

Confirm the symptom

Heat pump is not producing warm air
Thermostat shows heating mode but no heat
System runs but room temperature doesn't rise

Tools and prep

Thermostat manual
Screwdriver
Vacuum cleaner
Circuit breaker panel access
Safety gloves
Flashlight

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 settings are correct.
Means: Thermostat is functioning properly.
Next: Check power supply.
Check Power Supply
Do: Ensure the heat pump’s power switch is on and check the circuit breaker for any tripped switches.
Observe: Power is restored and the system powers on.
Means: Electrical supply is stable.
Next: Inspect air filter.
Inspect Air Filter
Do: Remove and examine the air filter for dirt or blockage.
Observe: Air filter is clean or dirty.
Means: A dirty filter can restrict airflow and reduce heating efficiency.
Next: Clean or replace the filter if necessary.
Clean or Replace Filter
Do: Clean reusable filters with water and let them dry, or replace disposable filters with new ones.
Observe: Airflow improves after cleaning or replacing the filter.
Means: Improved airflow can restore heating performance.
Next: Check refrigerant levels.
Check Refrigerant Levels
Do: Listen for hissing sounds and inspect for ice buildup on the outdoor unit.
Observe: No hissing sounds and no ice buildup.
Means: Refrigerant levels are likely normal.
Next: Inspect thermostat connections.
Inspect Thermostat Connections
Do: Turn off power to the heat pump and remove the thermostat cover to check for loose or disconnected wires.
Observe: Wires are securely connected.
Means: Thermostat is properly connected to the system.
Next: Test system operation.
Test System Operation
Do: Turn the power back on and set the thermostat to a higher temperature to see if the heat pump starts heating.
Observe: Heat pump begins producing warm air.
Means: Issue is resolved.
Next: End

Common causes

Cause	Likelihood	Difficulty	Part often needed
Incorrect Thermostat Settings Thermostat not set to 'Heat' mode or incorrect temperature setting.	Common	Easy	None
Power Supply Issues Tripped circuit breaker or power switch turned off.	Common	Easy	None
Dirty Air Filter Blocked airflow reduces heating efficiency.	Common	Easy	Air filter
Low Refrigerant Levels Leak in the refrigerant system reduces heat transfer efficiency.	Sometimes	Hard	Refrigerant (requires professional)
Loose Thermostat Wires Disconnected wires prevent proper communication between thermostat and system.	Sometimes	Easy–Medium	Wire connectors
Faulty Defrost Timer Defrost cycle not functioning properly, leading to ice buildup.	Rare	Medium	Defrost timer
Malfunctioning Auxiliary Heat Emergency heat not engaging when needed.	Rare	Medium	Heating elements
Outdoor Unit Obstruction Debris or ice blocking the outdoor unit affects heat exchange.	Sometimes	Easy	None
Faulty Compressor Compressor not functioning, preventing heat generation.	Rare	Hard	Compressor
Thermostat Battery Low Weak batteries can cause erratic thermostat behavior.	Sometimes	Easy	Thermostat batteries

Parts matching

Common parts needed for heat pump not heating issues include:

Air filter
Thermostat batteries
Wire connectors
Refrigerant (professional installation required)
Defrost timer
Heating elements
Compressor

Always replace parts with the correct specifications for your heat pump model.

When to call a professional

System still doesn't heat after checking all basic issues
Refrigerant leak detected (hissing sound or ice buildup)
Compressor or defrost timer failure suspected
Thermostat wiring damage or complex electrical issues
Unusual noises or burning smells from the unit
Heat pump is over 10 years old and frequent repairs are needed

FAQ

Why is my heat pump running but not heating?

This can be due to a dirty air filter, incorrect thermostat settings, or low refrigerant levels. Check these common issues first.

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

Replace disposable filters every 1–3 months and clean reusable filters monthly for optimal performance.

Can I add refrigerant to my heat pump myself?

No, refrigerant handling requires professional tools and certification. Contact a licensed HVAC technician for refrigerant issues.

What should I do if my heat pump is making ice?

Turn off the system and allow the ice to melt. Check for refrigerant leaks or a faulty defrost timer, and contact a professional if the issue persists.

How can I tell if my thermostat is the problem?

Check for loose wires, replace batteries, and ensure settings are correct. If the thermostat still doesn't respond, it may need replacement.