Heat Pump Not Heating or Cooling (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, air filter, and power supply. If the outdoor unit isn't running, reset the circuit breaker. If the issue persists, the refrigerant or internal components may need professional inspection.

Confirm the symptom

No airflow from vents
Thermostat shows no error but room temperature doesn't change
Outdoor unit is silent or not running
System runs but doesn't heat/cool effectively
Thermostat is set correctly but no response

Tools and prep

Thermostat screwdriver
Vacuum or replacement air filter
Flashlight
Screwdriver set
Voltage tester
Turn off power at the circuit breaker before inspecting electrical components
Wear gloves and safety glasses when handling parts

Step-by-step troubleshooting

Check Thermostat Settings
Do: Verify the thermostat is set to 'Heat' or 'Cool' mode, with the correct temperature.
Observe: Thermostat shows correct settings but system doesn't respond.
Means: Thermostat may be faulty or not communicating with the system.
Next: Test thermostat wiring or replace batteries.
Inspect Air Filter
Do: Remove and examine the air filter for dirt or blockage.
Observe: Filter is dirty or clogged.
Means: Restricted airflow reduces efficiency and system performance.
Next: Replace or clean the filter and test the system.
Check Power Supply
Do: Ensure the outdoor unit's power switch is on and the circuit breaker hasn't tripped.
Observe: Breaker is tripped or power switch is off.
Means: Power interruption prevents the system from operating.
Next: Reset the breaker or switch and restart the system.
Inspect Outdoor Unit
Do: Look for ice buildup, debris, or obstructions around the unit.
Observe: Unit is blocked or frozen.
Means: Blocked airflow or ice can hinder heat exchange.
Next: Clear debris or defrost the unit and wait for it to restart.
Test Emergency Heat
Do: If in heating mode, switch the thermostat to 'Emergency Heat' and check for response.
Observe: Emergency heat works but regular mode does not.
Means: Auxiliary heat strips may be functional, but the heat pump is not operating.
Next: Check refrigerant levels or contact a professional.
Check for Error Codes
Do: Review the thermostat or system control panel for error codes.
Observe: Error code is displayed.
Means: Specific error codes indicate system faults.
Next: Refer to the user manual or contact a technician.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Dirty Air Filter Blocked airflow reduces system efficiency and performance.	Common	Easy	Air filter
Thermostat Issues Faulty wiring, batteries, or programming can prevent proper operation.	Common	Easy–Medium	Thermostat batteries or replacement unit
Tripped Circuit Breaker Power interruption stops the system from running.	Common	Easy	None
Low Refrigerant Levels Leakage or insufficient refrigerant prevents proper heat transfer.	Sometimes	Hard	Refrigerant recharge (professional service)
Frozen Outdoor Unit Excess ice or debris blocks airflow and heat exchange.	Sometimes	Medium	Defrosting tools or deicer
Faulty Defrost System Malfunctioning defrost timer or sensor prevents automatic ice removal.	Sometimes	Hard	Defrost control board or sensor
Worn Compressor or Fan Motor Degraded components reduce system output or prevent operation.	Rare	Hard	Compressor or fan motor replacement

Parts matching

Common parts for heat pump issues include:

Air filter
Thermostat batteries
Thermostat replacement unit
Defrost control board
Refrigerant recharge kit (for minor leaks)

For refrigerant leaks or compressor issues, contact a licensed HVAC technician.

When to call a professional

System doesn't respond after checking all basic components
Error codes persist or recur after resets
Refrigerant levels are low or there's a suspected leak
Outdoor unit is frozen and defrosting doesn't resolve the issue
Unusual noises or burning smells from the unit
System runs continuously but provides no heating or cooling

FAQ

Why is my heat pump running but not heating my home?

This could be due to low refrigerant, a faulty compressor, or a malfunctioning defrost system. Check for error codes and ensure the outdoor unit is clear of ice and debris.

Can a dirty air filter cause a heat pump to stop working?

Yes, a clogged filter restricts airflow, reducing efficiency and potentially triggering system shutdowns. Replace or clean the filter regularly.

How do I know if my heat pump needs refrigerant?

Signs include reduced cooling/heating, ice on the outdoor unit, or error codes. Refrigerant issues require professional diagnosis and recharge.

What should I do if my heat pump freezes up?

Turn off the system, clear debris, and allow it to defrost naturally. If freezing recurs, check the defrost system or contact a technician.

Is emergency heat the same as regular heating?

No, emergency heat uses auxiliary electric resistance heating. It's less efficient and intended for backup use only.