Heat Pump Not Running in Heat Mode (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 heat pump is on, and verify the emergency heat setting. If the issue persists, inspect the air filter and circuit breaker.

Confirm the symptom

Heat pump works in cooling mode but not in heating mode
Thermostat shows heat call but no heat output
No airflow from vents when in heat mode
Heat pump makes noise but doesn't produce heat
Emergency heat works but heat pump doesn't

Tools and prep

Thermostat manual
Screwdriver
Flashlight
Multimeter
Ladder
Safety gloves
Turn off power to the heat pump at the circuit breaker
Check for any visible damage or tripped breakers

Step-by-step troubleshooting

Check Thermostat Settings
Do: Verify the thermostat is set to 'Heat' mode and the temperature is higher than the room temperature.
Observe: Thermostat displays correct mode and temperature.
Means: Thermostat is functioning correctly.
Next: If settings are correct, proceed to step 2.
Inspect Emergency Heat Setting
Do: Check if the emergency heat setting is activated on the thermostat.
Observe: Emergency heat indicator is on or off.
Means: Emergency heat may be overriding the heat pump.
Next: If emergency heat is on, turn it off and wait 5 minutes.
Check Air Filter
Do: Locate and inspect the air filter for dirt or blockage.
Observe: Air filter is clean or dirty.
Means: A dirty filter can restrict airflow and affect heat production.
Next: If the filter is dirty, replace or clean it and test the heat pump.
Verify Circuit Breaker
Do: Check the circuit breaker for the heat pump to ensure it hasn't tripped.
Observe: Breaker is in the 'On' position.
Means: Power is reaching the heat pump.
Next: If the breaker is tripped, reset it and monitor the heat pump.
Test Heat Pump Operation
Do: Turn the thermostat to a higher temperature and observe the heat pump.
Observe: Heat pump starts and produces heat.
Means: Heat pump is functioning correctly.
Next: If the heat pump does not start, proceed to step 5.
Check for Error Codes
Do: Look for any error codes on the thermostat or heat pump control panel.
Observe: Error code is displayed or not.
Means: Error codes can indicate specific issues with the heat pump.
Next: If an error code is present, consult the heat pump manual for troubleshooting steps.
Inspect Defrost Mode
Do: Check if the heat pump is in defrost mode, which temporarily stops heating.
Observe: Heat pump is in defrost mode or not.
Means: Defrost mode is a normal operation cycle.
Next: Wait for the defrost cycle to complete and test the heat pump again.
Check Refrigerant Levels
Do: Listen for any hissing sounds and inspect for refrigerant leaks.
Observe: No hissing sounds or visible leaks.
Means: Refrigerant levels are likely adequate.
Next: If a leak is suspected, contact a professional HVAC technician.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Incorrect Thermostat Settings Thermostat not set to 'Heat' mode or incorrect temperature setting.	Common	Easy	None
Emergency Heat Activated Emergency heat setting overrides the heat pump operation.	Common	Easy	None
Dirty Air Filter Restricted airflow reduces heat output and efficiency.	Common	Easy	Air filter
Tripped Circuit Breaker Power interruption due to electrical overload or fault.	Sometimes	Easy	None
Refrigerant Leak Low refrigerant levels prevent proper heat transfer.	Sometimes	Hard	Refrigerant
Defrost Mode Activation Heat pump enters defrost mode to remove ice buildup.	Sometimes	Easy	None
Faulty Auxiliary Heat Strip Auxiliary heat not engaging when needed.	Rare	Medium	Heat strip
Thermostat Malfunction Thermostat fails to send signals to the heat pump.	Rare	Medium	Thermostat
Outdoor Unit Issues Frozen coils or mechanical failure in the outdoor unit.	Rare	Hard	Outdoor unit repair
Control Board Failure Internal control board malfunction prevents heat pump operation.	Rare	Hard	Control board

Parts matching

Common parts needed for a heat pump not running in heat mode include:

Air filter
Thermostat
Heat strip
Refrigerant
Control board
Outdoor unit components

Always refer to your heat pump's manual for specific part compatibility and installation instructions.

When to call a professional

If the heat pump still doesn't run after checking all settings and components
If you suspect a refrigerant leak or electrical issues
If the outdoor unit is frozen or shows signs of mechanical failure
If error codes persist or recur after troubleshooting
If the heat pump is over 10 years old and frequent repairs are needed

FAQ

Why is my heat pump running but not producing heat?

This could be due to incorrect thermostat settings, a dirty air filter, or the heat pump being in defrost mode. Check these components first.

Can a tripped circuit breaker cause the heat pump to stop heating?

Yes, a tripped breaker can cut power to the heat pump, preventing it from operating in heat mode. Reset the breaker and test the system.

What should I do if the emergency heat is on but the heat pump isn't working?

Turn off the emergency heat setting and wait 5 minutes. If the heat pump still doesn't operate, check the thermostat and circuit breaker.

How do I know if my heat pump needs refrigerant?

Listen for hissing sounds and check for reduced heat output. If suspected, contact a professional HVAC technician for a refrigerant check.

Is it normal for the heat pump to cycle on and off frequently in heat mode?

Frequent cycling can indicate an issue with the thermostat, airflow, or refrigerant levels. Investigate these areas for potential problems.