Heat Pump Outdoor Unit Not Running

If the outdoor heat-pump unit is not running when you expect it to, check thermostat settings, system mode, power, and obvious external obstructions before calling for service.

Do not open the outdoor cabinet.

Safety: For smoke or suspected fire, leave the building, stay outside, and call 911 from a safe location. For repeated breaker trips, burning smells, sparking, or damaged wiring without signs of fire, stop troubleshooting; switch the thermostat Off only if safe and call a qualified technician. Do not open the cabinet, reach through the fan grille, or bypass equipment protections.

Confirm the System Is Actually Calling

Check:

• Heat or Cool mode
• setpoint
• thermostat schedule
• system delay after mode change
• error/fault display

Some systems deliberately delay compressor restart for several minutes.

Is It in a Mode Where the Outdoor Fan Stops?

During some defrost sequences, the outdoor fan can stop temporarily.

Do not diagnose "outdoor unit failed" from a brief defrost event.

Heat pump defrost cycle

Check the Breaker Once

Only consider one reset if you can identify the correct HVAC breaker, the panel and surrounding area are dry, there is no smoke, burning smell, sparking, unusual heat, or visible damage, and the equipment instructions permit it. Use only the breaker handle; never remove the panel cover or open equipment cabinets. If uncertain, leave it to a qualified technician.

If it trips again:

stop resetting it.

Repeated trips need electrical/mechanical diagnosis.

Source: Carrier - Heat Pump Troubleshooting

Check for Snow or Debris

Make sure the unit is not physically blocked by:

• packed snow
• leaves
• branches
• objects against discharge

Do not reach through the grille.

Why Would the Outdoor Unit Stop?

Possible causes include:

• thermostat/control issue
• electrical fault
• contactor/control component
• compressor protection
• fan motor
• sensor
• defrost/control logic
• refrigerant-system fault
• equipment safety lockout

Several require similar diagnostics.

What If the Indoor Fan Still Runs?

The indoor blower can run while the outdoor unit is off.

That can circulate room-temperature air and create a "blowing cold air" complaint in heating mode.

Heat pump blowing cold air

What If the Outdoor Unit Hums but the Fan Does Not Turn?

Switch the thermostat Off only if safe and arrange service.

Do not push or spin the fan by hand through the grille and do not open the cabinet to test electrical components.

Can You Fix It Yourself?

Homeowner-safe work is limited to:

• thermostat check
• accessible filter check
• visible breaker check
• loose external debris/snow

Anything beyond that commonly involves electrical, control, motor, or refrigerant diagnostics.

For mode-specific checks, see heat pump not heating and heat pump not cooling. Review repair costs when comparing estimates.

Get the Outdoor Unit Diagnosed

If the outdoor unit does not resume normal operation after basic checks, schedule professional heat-pump service.