Heat Pump Not Heating to Set Temperature (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, air filter, and outdoor unit for obstructions. If the issue persists, verify the heat pump's emergency heat setting and test the system's defrost cycle.

Confirm the symptom

Thermostat is set above room temperature
Heat pump runs but doesn't reach desired temperature
Outdoor unit is not blowing hot air
Indoor unit fan runs but no warm air
System cycles on and off frequently

Tools and prep

Screwdriver set
Vacuum cleaner
Thermometer
Safety gloves
Flashlight
Owner's manual

Step-by-step troubleshooting

Check Thermostat Settings
Do: Verify the thermostat is set to 'Heat' mode and the temperature is higher than the current room temperature.
Observe: Thermostat shows correct mode and temperature.
Means: Thermostat settings are correct.
Next: If settings are correct, proceed to step 2.
Inspect Air Filter
Do: Turn off the heat pump at the thermostat or circuit breaker. Remove and inspect the air filter for dirt or blockage.
Observe: Filter is clean or dirty.
Means: A dirty filter restricts airflow and reduces heating efficiency.
Next: Replace the filter if dirty. If clean, proceed to step 3.
Check Outdoor Unit
Do: Inspect the outdoor unit for ice buildup, debris, or obstructions. Clear any blockages with a soft brush or vacuum.
Observe: Outdoor unit is free of ice and debris.
Means: Obstructions can prevent proper heat exchange.
Next: If unit is clear, proceed to step 4.
Verify Emergency Heat
Do: Check if the thermostat has an 'Emergency Heat' setting and ensure it is not activated unless needed.
Observe: Emergency heat is off or on.
Means: Emergency heat is a backup and should not be used regularly.
Next: If emergency heat is on, turn it off. If off, proceed to step 5.
Test Defrost Cycle
Do: Monitor the outdoor unit during operation. If it's cold outside, check if the unit enters a defrost cycle to melt ice.
Observe: Outdoor unit periodically stops heating and starts defrosting.
Means: A faulty defrost cycle can reduce heating efficiency.
Next: If defrost cycle is not working, proceed to step 6.
Check Refrigerant Levels
Do: Listen for hissing sounds or check for ice on refrigerant lines. Low refrigerant can cause poor heating.
Observe: No hissing sounds and no ice on refrigerant lines.
Means: Refrigerant levels are adequate.
Next: If refrigerant is low, contact a professional. If levels are fine, proceed to step 7.
Inspect Electrical Connections
Do: Turn off power to the heat pump at the circuit breaker. Check electrical connections for looseness or corrosion.
Observe: Connections are secure and dry.
Means: Loose or corroded connections can disrupt operation.
Next: If connections are secure, proceed to step 8.
Check for Error Codes
Do: Review the thermostat or heat pump for error codes displayed on the control panel.
Observe: Error codes are present or not.
Means: Error codes can indicate specific issues.
Next: Refer to the owner's manual for error code meanings. If unresolved, contact a professional.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Dirty air filter Restricts airflow and reduces heating efficiency.	Common	Easy	Air filter
Thermostat settings incorrect Improper mode or temperature setting prevents heating.	Common	Easy	None
Outdoor unit obstruction Debris or ice prevents proper heat exchange.	Common	Easy–Medium	None
Faulty defrost cycle Ice buildup on outdoor coil reduces efficiency.	Sometimes	Medium	Defrost control board
Low refrigerant Inadequate refrigerant reduces heat transfer.	Sometimes	Hard	Refrigerant
Loose electrical connections Interrupts power to components.	Sometimes	Medium	Wire connectors
Thermostat malfunction Incorrect temperature readings or signals.	Sometimes	Medium	Thermostat
Compressor failure Compressor not engaging to transfer heat.	Rare	Hard	Compressor

Parts matching

If you need replacement parts for your heat pump, consider these common items:

Air filter
Thermostat
Defrost control board
Refrigerant (must be handled by professional)
Wire connectors
Compressor (professional installation required)

Always refer to your heat pump's model number when ordering parts to ensure compatibility.

When to call a professional

If the heat pump still doesn't heat after checking all steps
If refrigerant levels are low or there are refrigerant leaks
If error codes persist or are not resolved
If the compressor or defrost control board is suspected to be faulty
If you're unsure about handling electrical components or refrigerant

FAQ

Can a dirty air filter really prevent my heat pump from heating properly?

Yes, a dirty air filter restricts airflow, reducing the system's efficiency and its ability to heat your home effectively.

What should I do if my heat pump is making a loud noise but not heating?

Turn off the system immediately and contact a professional, as loud noises can indicate mechanical issues like a failing compressor.

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

Check the air filter at least once a month during heavy use periods, and clean or replace it as needed.

Is it normal for the outdoor unit to freeze during cold weather?

Some frost is normal, but excessive ice or a unit that doesn't defrost properly indicates a problem with the defrost cycle.

Can I use emergency heat as my primary heating source?

No, emergency heat is a backup system and is less efficient. Use it only when the heat pump is not functioning.