Heat Pump Outside Unit Not Running (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 supply is on, and inspect the circuit breaker. If the unit still doesn't run, try resetting the unit or checking for error codes.

Confirm the symptom

Outside unit does not turn on when the thermostat calls for heating or cooling
No sound or vibration from the outdoor unit
Indoor unit is running but the outdoor unit is silent

Tools and prep

Voltage tester
Screwdriver set
Thermometer
Owner's manual
Safety gloves and goggles
Flashlight
Ladder (if unit is high)

Step-by-step troubleshooting

Check Thermostat Settings
Do: Verify the thermostat is set to 'Heat' or 'Cool' and the temperature is set to trigger the system.
Observe: Thermostat settings match the desired operation mode.
Means: Thermostat is correctly configured.
Next: Check power supply to the unit.
Check Power Supply
Do: Look at the circuit breaker or fuse box to see if the heat pump's circuit is tripped or blown.
Observe: Circuit breaker is on and not tripped.
Means: Power is reaching the unit.
Next: Inspect the disconnect switch near the unit.
Inspect Disconnect Switch
Do: Locate the disconnect switch near the outdoor unit and ensure it is in the 'On' position.
Observe: Switch is in the 'On' position and not damaged.
Means: Power is being supplied to the unit.
Next: Check for error codes on the unit's control panel.
Check for Error Codes
Do: Look at the unit's control panel for any blinking lights or error codes.
Observe: Error code is displayed or blinking lights indicate an issue.
Means: Unit has detected a problem that needs attention.
Next: Consult the owner's manual for error code meanings.
Reset the Unit
Do: Turn off the power to the unit at the circuit breaker for 30 seconds, then restore power.
Observe: Unit powers on and starts operating normally.
Means: The issue may have been a temporary electrical fault.
Next: Monitor the unit for continued operation.
Inspect for Obstructions
Do: Check the outdoor unit for debris, leaves, or ice buildup that may block airflow.
Observe: Unit is clear of obstructions and has proper airflow.
Means: No physical blockage is preventing operation.
Next: Check the temperature around the unit.
Check Unit Temperature
Do: Ensure the outdoor temperature is within the unit's operating range (typically above 32°F or 0°C for heating).
Observe: Temperature is within the unit's operating range.
Means: Unit can operate under current conditions.
Next: Contact a professional if the unit still does not run.

Common causes

Cause	Likelihood	Difficulty	Part often needed
Tripped Circuit Breaker The unit's circuit may have tripped due to an electrical overload or short.	Common	Easy	None
Incorrect Thermostat Settings The thermostat may be set to 'Off' or an incorrect mode.	Common	Easy	None
Frozen Outdoor Unit Ice buildup can prevent the unit from starting or operating properly.	Sometimes	Easy–Medium	Deicing kit
Dirty Air Filter A clogged air filter can restrict airflow and cause the unit to shut down.	Sometimes	Easy	Air filter
Low Refrigerant Low refrigerant levels can cause the unit to malfunction or not start.	Sometimes	Hard	Refrigerant
Failed Outdoor Fan Motor A faulty fan motor can prevent the unit from running or cause it to make unusual noises.	Sometimes	Medium	Outdoor fan motor
Defective Control Board A malfunctioning control board can prevent the unit from receiving signals to start.	Rare	Hard	Control board
Thermostat Wiring Issues Loose or damaged wiring at the thermostat can prevent signals from reaching the unit.	Rare	Medium	Thermostat wiring kit
Refrigerant Leak A refrigerant leak can cause the unit to underperform or not start at all.	Rare	Hard	Refrigerant and repair kit
Defective Compressor A failed compressor can prevent the unit from starting or cause it to make loud noises.	Rare	Hard	Compressor

Parts matching

Common parts needed for a heat pump outside unit not running include:

Circuit breaker
Thermostat
Air filter
Deicing kit
Outdoor fan motor
Control board
Refrigerant

Always refer to the manufacturer's specifications and consult a professional for refrigerant-related issues or complex repairs.

When to call a professional

The unit still does not run after checking all power sources and settings
Error codes persist or indicate a serious issue
You detect a refrigerant leak or smell
The unit makes loud or unusual noises
You suspect a failed compressor or control board
The outdoor temperature is within the operating range but the unit still does not start

FAQ

Why is my heat pump outside unit not turning on?

Possible reasons include a tripped circuit breaker, incorrect thermostat settings, or a frozen outdoor unit. Check these common issues first.

Can a dirty air filter cause the outdoor unit to stop running?

Yes, a clogged air filter can restrict airflow and cause the unit to shut down. Clean or replace the filter to resolve this issue.

What should I do if I see an error code on the unit's control panel?

Consult the owner's manual for the specific error code meaning. Some codes may require professional attention.

Is it normal for the outdoor unit to not run in very cold weather?

Heat pumps typically operate efficiently down to about 32°F (0°C). Below this temperature, auxiliary heating may be needed, and the unit may not run as frequently.

How can I prevent my outdoor unit from freezing?

Ensure the unit is clear of debris and has proper airflow. Consider using a deicing kit if ice buildup is a recurring issue.