Heat pump not working: common causes, what you can safely check and when to call for service

Quick Answer

Identify why your heat pump is not working by checking for a lack of airflow or unusual noises from the outdoor compressor. MyHomeLobby recommends verifying the power supply to the outdoor unit first, since a blown fuse often mimics a total mechanical failure.

A heat pump system can fail to produce heat even when the fan runs because the reversing valve is stuck in the wrong position.

Reasons your heat pump not working

A heat pump fails to work because of power loss, faulty controls, or mechanical failure. Common issues include a tripped circuit breaker, a malfunctioning thermostat, or a failed compressor. You can understand how heat pumps work by checking the power supply, the control settings, and the physical state of the outdoor unit.

Common mini split issues

• A tripped circuit breaker cuts electricity to the system and stops all operation.
• The thermostat fails to send a signal to the unit when the temperature drops.
• A failed compressor prevents the system from moving refrigerant to generate heat.
• The heat mode setting must be active for the unit to produce warm air.
• An ac heat pump not working often stems from a clogged filter or blocked airflow.

Heat mode tells your system to warm the house

Heat mode is the specific setting that directs the heat pump to extract heat from the outside air. You activate it using your thermostat to switch from cooling to heating. You must ensure this is selected correctly to troubleshoot why your home is not getting warm.

Why is my heat pump not working?

Your system may stop because the electrical supply is interrupted or the thermostat fails to communicate with the hardware. Mechanical issues like a broken compressor or a refrigerant leak also stop the cycle. Check your breaker box and thermostat settings first to rule out simple power or configuration errors.

Why is my air conditioner heat pump failing?

Your air conditioner heat pump is failing if the system produces weak airflow, produces inconsistent temperatures, or makes loud grinding noises. These signs indicate internal mechanical wear or a refrigerant leak. You can see how a capacitor supports the motor and check the thermostat settings and outdoor unit clearance to rule out simple configuration errors before assuming a hardware failure.

Pump failure symptoms

• The indoor unit produces warm air during the cooling cycle.
• The outdoor compressor makes a loud clicking or grinding sound.
• Ice builds up on the evaporator coil during operation.
• A refrigerant leak causes the air conditioner heat pump not working because the system lacks the fluid to move heat.
• The system shuts down frequently due to a tripped circuit breaker.

Signs of a failing pump

A failing pump often involves a leak in the refrigerant lines or a clogged evaporator coil. The evaporator coil transfers heat from the indoor air to the refrigerant. If this coil remains dirty, the system loses efficiency and you can compare air to water systems.

Reset settings and refrigerant charging

Many systems include emergency heat to provide warmth when the heat pump cannot operate. You can reset the system settings to clear temporary software errors. A technician must charge the refrigerant levels to the correct pressure if a leak occurs.

Emergency heat provides a backup source of warmth

Emergency heat is a secondary heating method that activates when the heat pump cannot provide enough warmth. It typically uses electric resistance coils to generate heat directly. Knowing this helps you decide if you need to turn on a backup system during extreme cold.

Safe checks for your heat pump

You can safely check the power switch, the air filter, and the thermostat settings. These components often cause a heat not working heat pump issue without requiring professional repair. Before calling a technician, check how ductwork limits performance to see if a simple manual adjustment restores your home heating.

1. Locate the power switch on the side of the indoor unit to see if the toggle remains in the on position.
2. Remove the air filter to check for dust buildup that restricts airflow.
3. Inspect the thermostat display to see if the current temperature setting is higher than the room temperature.
4. Check the outdoor unit to see if debris blocks the fan.

Ductless heat pump checklist

Component	Action	Result
Power Switch	Turn to on	Unit lights up
Air Filter	Clean or replace	Airflow improves

What can I safely check myself?

Users can check the thermostat to see if the system is set to heat mode. You can also check the circuit breaker to see if it tripped. These actions help determine if the problem is a simple setting or a mechanical failure in the pump units. Pump units are the mechanical components that move refrigerant through the system to transfer heat.

How do I switch my system to heat mode?

To switch my system to heat mode, you must adjust the thermostat to a temperature higher than the current room temperature. Most thermostats require you to select a heat icon or a specific heating setting to activate the heat pump. The system starts when the thermostat detects the indoor temperature is below your set point.

Thermostat operation and heat mode symbols

A thermostat decides when to trigger the heat pump based on the temperature difference between the set point and the current room air. Some systems use a heat pump to blend air from the indoor unit with outside air to reach the desired temperature. You can compare heat pumps with furnaces by looking for a “Heat” label or a flame symbol on the display screen.

Mini split systems as a viable alternative

A mini split system installs as a ductless unit to heat specific zones without using central air ducts. A mini split system is a type of heating and cooling unit that provides air to specific rooms without using ducts. This system unlocks individual temperature control for different rooms. Each indoor head unit operates independently to heat the space it serves.

Emergency steps when heat fails in extreme cold

Switch your system to emergency heat immediately if your heat pump fails in extreme cold. Most heat pumps include an auxiliary heat source, such as electric resistance strips or a gas furnace, to maintain indoor temperatures when the outdoor unit cannot extract enough heat from the air.

Electric heat strips and gas furnaces

Identify the specific auxiliary heat source your model uses. Some systems use electric heat strips that activate when the outdoor temperature drops below a certain threshold. Other systems utilize a secondary gas furnace to provide supplemental warmth.

Thermostat settings and manual overrides

Check your thermostat to see if the emergency heat mode is active. Some thermostats have a dedicated switch or a menu setting to engage this backup. If the thermostat does not trigger the auxiliary heat, the system may require a manual override at the indoor air handler.

What to do if the heat stops?

Verify the power supply to the outdoor unit and the indoor furnace. Check the circuit breaker panel to see if a switch tripped during the cold snap. Ensure the outdoor unit remains clear of heavy snow or ice buildup that might block airflow.

Steps to take when your heat pump is not working

Troubleshooting and repair checklist

1. Locate your heat pump's manual and installation records. Find the physical manual or digital files provided during installation. Having these documents ready ensures you have the correct model specifications for the next checks.
2. Verify the thermostat power and temperature settings. Check that the thermostat display is active and set to the correct heating mode. A blank screen or incorrect mode means the issue is with the controls.
3. Inspect the circuit breaker and outdoor power supply. Look at your electrical panel to see if the heat pump breaker has tripped. Flip it back on; if it trips again immediately, the unit has a serious electrical fault.
4. Check the outdoor unit for debris or ice. Clear away leaves, snow, or ice from the outdoor unit's coils. If the unit remains unresponsive after clearing the area, the problem is likely internal.
5. Contact a qualified technician for a formal inspection. Call a certified HVAC technician to diagnose the system. If they identify a component failure, request a written quote before authorizing any major repairs.

Frequently asked questions