Heat Pump Not Heating? 15 Common Causes for BC Homes

Heat Pump Not Heating: What Should You Check First?

Before requesting service, complete these basic checks:

1. Confirm the thermostat is set to Heat.
2. Set the temperature above the current room temperature.
3. Set the fan to Auto unless the equipment instructions say otherwise.
4. Check whether the thermostat displays a fault or warning message.
5. Inspect the air filter and clean or replace it if required.
6. Confirm supply registers and return grilles are open and unobstructed.
7. Check that ductless indoor-unit filters and air openings are clear.
8. Look at the outdoor unit without opening the cabinet.
9. Remove loose leaves, snow or debris around the equipment.
10. Wait for any normal control delay stated in the manufacturer’s manual.

Do not assume the system has failed only because the supply air feels less hot than air from a gas furnace. Heat pumps often maintain temperature using longer cycles and moderately warm airflow.

The important question is whether the heat pump is maintaining the selected indoor temperature.

Is the Heat Pump Operating Normally or Does It Need Repair?

Cause 1: Incorrect Thermostat or Operating Mode

A thermostat setting can prevent an otherwise functional heat pump from heating.

Check that:

• The operating mode is set to Heat
• The selected temperature is above room temperature
• The fan is set appropriately
• The schedule is not lowering the temperature unexpectedly
• Vacation or away mode is not active
• Emergency Heat has not been selected accidentally
• The thermostat has power
• The thermostat display is not showing an equipment fault

Heat Mode Versus Auto Mode

Auto mode allows some systems to switch between heating and cooling. During unusual weather or when the thermostat is affected by sunlight, cooking or a fireplace, the system may not respond as expected.

Use the dedicated Heat mode during the heating season unless the building requires automatic changeover.

Thermostat Location

A thermostat may read the wrong room condition when it is affected by:

• Direct sunlight
• A supply register
• An exterior-door draft
• A fireplace
• Kitchen heat
• Electronic equipment
• An unusually warm or cold wall

Large Temperature Setbacks

A large thermostat increase can cause the heat pump to operate at maximum capacity or activate backup heating.

Heat pumps often perform more efficiently and comfortably when maintaining a relatively stable temperature.

Cause 2: A Dirty or Restrictive Air Filter

A dirty filter reduces airflow through the indoor equipment.

Restricted airflow can cause:

• Reduced heating capacity
• Long operating cycles
• Weak airflow from registers
• Higher energy use
• Indoor-coil temperature problems
• Equipment faults
• Increased blower stress

Central Heat Pump Filters

A central system may use a disposable filter, washable filter, media cabinet or electronic air cleaner.

Check that:

• The filter is installed in the correct direction
• The filter is the correct size
• The filter is not heavily loaded with dust
• The filter access panel is closed properly
• A highly restrictive filter has not been installed without airflow review

Ductless Heat Pump Filters

Ductless indoor units usually have reusable mesh filters.

Turn the indoor unit off and follow the manufacturer’s instructions for removing and cleaning them. Allow washable filters to dry before reinstalling them.

A clean filter does not prove the indoor coil and blower wheel are clean. Internal contamination may still reduce airflow.

Cause 3: Restricted Indoor Airflow

The heat pump needs enough air moving through the indoor coil and occupied rooms.

Common Ducted Airflow Restrictions

• Closed supply registers
• Blocked return grilles
• Furniture over floor registers
• Crushed flexible ducts
• Closed balancing dampers
• Undersized return ducts
• Dirty indoor coil
• Incorrect blower speed
• Restrictive filter cabinet

Closing registers to save energy can increase duct pressure and reduce total system airflow.

Common Ductless Airflow Restrictions

• Furniture directly below the indoor unit
• Curtains blocking the discharge
• Dirty filters
• Dirty blower wheel
• Dirty indoor coil
• Incorrect louver direction
• Indoor unit installed in a poor location

A ductless unit installed in an open living area may not deliver enough heat into closed bedrooms or around several corners.

Cause 4: The Outdoor Unit Is Blocked

The outdoor heat exchanger needs free airflow to collect heat from outdoor air.

Common obstructions include:

• Leaves
• Snow
• Plastic bags
• Vegetation
• Fence panels
• Stored items
• Roof runoff and ice
• Grass clippings
• Construction dust

Keep the manufacturer-required clearances around the unit.

Do not place a full cover over an operating heat pump. The outdoor unit must exchange air throughout winter.

Safe Outdoor Check

From outside the cabinet, look for:

• Heavy ice
• Blocked fan opening
• Loose panels
• Severe vibration
• Unusual grinding sounds
• Debris pressed against the coil
• Defrost water trapped around the base

Do not open the electrical panel or insert tools through the fan guard.

Cause 5: Normal Defrost or a Defrost-System Failure

Frost can form on the outdoor coil during heating operation, especially in cool and damp weather.

The heat pump periodically enters defrost mode to melt the frost.

Normal Defrost Behaviour

During a normal defrost cycle:

• The outdoor fan may stop
• The compressor sound may change
• Steam may rise from the outdoor unit
• Water may drain beneath the unit
• Indoor supply air may feel temporarily cooler
• Auxiliary heat may operate

The unit should return to normal heating after the cycle.

Possible Defrost Problems

Professional inspection may be needed when:

• The outdoor coil remains covered in heavy ice
• The system repeatedly enters defrost
• The outdoor fan strikes ice
• The unit does not return to heating
• Ice forms around the base and blocks drainage
• The home loses substantial temperature during repeated cycles

Possible causes include failed sensors, damaged controls, low refrigerant, restricted airflow, fan problems, reversing-valve faults or unsuitable drainage.

Do not chip ice from the coil with sharp tools.

Cause 6: Auxiliary or Backup Heat Is Not Operating Correctly

A heat pump may use backup heat during colder conditions, thermostat recovery or defrost.

Electric Auxiliary Heat

A central electric air handler may contain resistance heating elements.

Backup heating may fail because of:

• A tripped breaker
• A failed heating element
• A damaged sequencer or relay
• A thermostat configuration problem
• A control-board fault
• A wiring problem
• A safety-limit condition

The heat pump may continue running while the home fails to reach temperature because the expected backup capacity is missing.

Emergency Heat

Emergency Heat is different from automatic auxiliary heat.

• Auxiliary heat is enabled automatically when additional capacity is required.
• Emergency Heat is normally a manual mode used when the heat pump compressor cannot operate.

Do not use Emergency Heat as a routine heating setting unless instructed by a technician or the equipment manual.

Cause 7: Electrical Power or Wiring Problem

A heat pump uses separate electrical circuits and controls for the outdoor unit, indoor equipment, thermostat and backup heat.

Possible electrical causes include:

• Tripped breaker
• Open disconnect
• Blown fuse
• Loose electrical connection
• Failed contactor
• Damaged capacitor on equipment that uses one
• Low or unstable voltage
• Failed control transformer
• Communication-wiring problem
• Damaged control board

Do Not Repeatedly Reset a Breaker

A breaker may trip because of a compressor fault, motor problem, damaged wiring, electrical short or unsuitable circuit condition.

Repeated resetting can increase damage and create a safety risk.

Request Urgent Service When:

• The breaker trips immediately
• There is a burning smell
• You hear buzzing or electrical arcing
• Electrical components are wet
• Wiring appears damaged
• The disconnect or panel is discoloured

Cause 8: Dirty Indoor or Outdoor Coils

Heat pumps transfer heat through indoor and outdoor coils.

Dirt on either coil reduces heat transfer and airflow.

Dirty Indoor Coil Symptoms

• Weak airflow
• Reduced heating
• Long operating cycles
• Indoor coil icing during cooling
• Unusual odours
• Higher blower speed

Dirty Outdoor Coil Symptoms

• Reduced heating capacity
• Long operating cycles
• Frequent defrost
• Compressor stress
• High energy use
• Equipment fault codes

Homeowners can remove loose debris from around the equipment. Internal coil cleaning and cabinet disassembly should follow manufacturer procedures and may require professional service.

High-pressure washing can bend coil fins or damage electrical components.

Cause 9: Low Refrigerant or a Refrigerant Leak

Refrigerant is not normally consumed during heat pump operation.

A low charge may indicate:

• A refrigerant leak
• An incorrect installation charge
• A previous incomplete repair
• Damaged refrigerant piping
• A leaking indoor or outdoor coil
• A flare or brazed-joint problem

Possible Refrigerant Problem Signs

• Reduced heating and cooling capacity
• Long operating cycles
• Indoor or outdoor coil icing
• Repeated fault codes
• Unusual refrigerant-pipe temperatures
• Oil residue near refrigerant connections
• Compressor overheating

Low airflow can create symptoms similar to a refrigerant problem. A technician should test airflow and refrigeration performance rather than adding refrigerant based only on weak heating.

Adding Refrigerant Is Not a Complete Leak Repair

When a leak is confirmed, the repair process may include:

1. Locating the leak
2. Evaluating whether the component is repairable
3. Recovering refrigerant where required
4. Repairing or replacing the leaking component
5. Pressure testing
6. Evacuating the system
7. Charging it according to manufacturer requirements
8. Confirming operation

Cause 10: Reversing-Valve Problem

The reversing valve changes refrigerant direction so the heat pump can switch between heating and cooling.

A valve or control problem may cause the system to:

• Remain in cooling mode
• Fail to switch fully into heating
• Produce weak heating
• Make an unusual refrigerant sound
• Show a pressure or temperature fault

The cause may involve:

• The reversing valve
• Valve coil
• Control-board output
• Thermostat wiring
• Refrigerant pressures
• Mechanical valve damage

Diagnosis requires electrical and refrigeration measurements. A reversing valve should not be condemned from supply-air temperature alone.

Cause 11: Failed Sensor, Thermostat or Control Board

Modern heat pumps rely on temperature sensors, pressure protection, inverter controls and communication between indoor and outdoor equipment.

A failed or inaccurate sensor may affect:

• Compressor speed
• Defrost timing
• Fan operation
• Backup heating
• System changeover
• Low-temperature protection

Possible Control-System Symptoms

• Fault codes
• Intermittent operation
• Indoor and outdoor units not communicating
• Defrost starting too often or not starting
• Fan operating without compressor heating
• Unexpected system shutdown
• Incorrect thermostat temperature

Record the fault code before turning power off. The code may help the technician identify the affected circuit or operating condition.

Do not repeatedly clear fault history before service.

Cause 12: Indoor Blower or Outdoor Fan Problem

The indoor blower moves heat into the home. The outdoor fan moves air through the outdoor coil.

Indoor Blower Problems

Possible causes include:

• Dirty blower wheel
• Failed motor
• Incorrect speed setting
• Control-board failure
• Loose wiring
• High static pressure
• Damaged fan wheel

If the indoor coil becomes hot but the blower does not move enough air, the system may trip a temperature or pressure protection.

Outdoor Fan Problems

Possible causes include:

• Failed motor
• Damaged blade
• Ice blocking the fan
• Control-board fault
• Loose connection
• Debris inside the cabinet

The outdoor fan may stop during a normal defrost cycle. It should resume when defrost ends.

Turn the system off and request service if the fan is striking ice or the cabinet.

Cause 13: Compressor or Inverter Problem

The compressor circulates refrigerant and creates the pressure difference required to move heat.

Possible compressor-related symptoms include:

• Outdoor fan operates but no heating is produced
• Breaker trips
• Compressor attempts to start repeatedly
• Grinding or severe mechanical noise
• Inverter or compressor fault code
• Abnormal current
• System shuts down under load

Not every outdoor-unit failure means the compressor has failed. Similar symptoms can result from controls, wiring, sensors, fan problems, refrigerant conditions or power supply.

Repair or Replacement

The decision depends on:

• Equipment age
• Warranty coverage
• Cause of failure
• Condition of the indoor equipment
• Parts availability
• Refrigerant type
• Previous repair history
• Replacement-system compatibility

Cause 14: Duct Leakage or Air-Distribution Problem

A heat pump may produce adequate heat while the home remains uncomfortable because the heat is not reaching the rooms correctly.

Common distribution problems include:

• Disconnected ducts
• Leaking joints
• Crushed flexible duct
• Uninsulated attic or crawl-space ducts
• Closed dampers
• Undersized branch ducts
• Insufficient return air
• Poor airflow balancing
• Registers in unsuitable locations

Signs of a Duct Problem

• Some rooms are warm while others remain cold
• Airflow is much weaker at distant registers
• The mechanical room is warm but occupied rooms are not
• Whistling occurs at return grilles
• The blower runs loudly
• Attic, crawl-space or basement areas feel unusually warm

A new heat pump cannot correct every duct problem without modifications to the distribution system.

Cause 15: Equipment Sizing or Cold-Weather Capacity Limitation

A heat pump’s available heating capacity may decrease as outdoor temperature falls while the home’s heating requirement increases.

The system may struggle when:

• The heat pump is undersized
• The equipment was selected from square footage alone
• The home has high air leakage
• Insulation is limited
• The selected model loses substantial capacity in cold weather
• Backup heat is too small or unavailable
• Ductwork cannot deliver the required airflow
• The thermostat setting is increased sharply

Long Operation Does Not Automatically Mean the System Is Undersized

Variable-capacity heat pumps are designed to run for long periods at lower output.

Possible sizing concerns become stronger when:

• The indoor temperature falls steadily
• The system remains at maximum output
• Backup heat runs continuously
• The same problem occurs during predictable outdoor conditions
• Airflow and equipment operation have already been verified

A contractor should compare the building’s heat-load calculation with the selected heat pump’s capacity at relevant outdoor temperatures.

Ductless Heat Pump Not Heating

Ductless systems have several additional operating considerations.

Check Every Indoor Unit

Confirm that:

• The unit is in Heat mode
• The setpoint is above room temperature
• The filter is clean
• The louvers are open
• The remote-control batteries work
• The indoor unit displays no fault code
• The air intake and discharge are unobstructed

Multi-Zone Mode Conflicts

Many multi-zone systems require connected indoor units to operate in the same general mode.

One indoor unit set to cooling, dry or automatic mode may conflict with other units requesting heat. Exact behaviour depends on the manufacturer.

Set all active zones to Heat and review the equipment manual.

Indoor Unit Does Not Serve Closed Rooms

A wall-mounted indoor unit may heat an open living area while closed bedrooms remain cold.

This may be a distribution limitation rather than an equipment fault.

The solution may require:

• Additional indoor units
• Keeping doors open
• Retained baseboard heating
• A short concealed duct system
• Room-by-room load and airflow review

Ductless Water or Ice Problems

Water leaking from an indoor unit may indicate:

• Blocked condensate drain
• Failed condensate pump
• Incorrect drain slope
• Dirty indoor coil
• Frozen coil

Turn the system off if water may contact electrical components or damage the building.

Dual-Fuel Heat Pump Not Heating

A dual-fuel system combines a heat pump with a gas furnace. The problem may be in either heating source or in the controls that change between them.

Possible Dual-Fuel Problems

• Incorrect outdoor changeover temperature
• Thermostat configuration error
• Heat pump lockout set too high
• Furnace lockout set incorrectly
• Failed outdoor-temperature sensor
• Furnace ignition failure
• Gas supply problem
• Furnace venting or condensate issue
• Heat pump defrost-control problem
• Indoor blower or shared-control fault

Do Not Attempt Gas-System Repairs

If the furnace fails to ignite or displays a gas-related fault, use a qualified gas technician.

Turn the system off and request urgent service when you smell gas, suspect combustion products or a carbon monoxide alarm activates.

Safe Checks Homeowners Can Complete

• Confirm Heat mode and thermostat setpoint.
• Check for schedules, vacation mode or Emergency Heat.
• Record fault codes.
• Inspect and clean approved reusable filters.
• Replace disposable filters when dirty.
• Open supply registers.
• Clear return grilles.
• Keep ductless indoor units unobstructed.
• Remove loose leaves and snow around the outdoor unit.
• Check whether heavy ice remains after defrost.
• Listen for new or severe mechanical sounds.
• Check for visible water leaks.
• Review the manufacturer’s operating manual.

Checks Homeowners Should Not Complete

• Opening electrical panels
• Testing live voltage
• Adding refrigerant
• Bypassing safety controls
• Forcing contactors or relays
• Chipping ice from coils
• Opening the sealed refrigeration system
• Attempting gas-furnace repairs
• Repeatedly resetting a tripped breaker

When Does a Heat Pump Need Urgent Service?

Turn the equipment off and request urgent professional service when:

• There is smoke or a burning smell
• The breaker repeatedly trips
• Water is reaching electrical equipment
• The outdoor fan is striking ice or the cabinet
• The compressor makes severe grinding or impact sounds
• Wiring appears damaged
• The system produces an electrical-arcing sound
• The outdoor unit is heavily iced and cannot operate
• A carbon monoxide alarm activates near a dual-fuel system
• You smell natural gas

Leave the building and contact the appropriate emergency or utility service if you smell gas or a carbon monoxide alarm indicates a possible dangerous condition.

What Should a Heat Pump Technician Inspect?

A professional diagnosis should identify the cause rather than replace parts based only on symptoms.

Depending on the system, the technician may inspect:

1. Thermostat settings and heating call
2. Fault-code history
3. Indoor and outdoor equipment communication
4. Filter and coil condition
5. Supply and return temperatures
6. Airflow and static pressure
7. Outdoor fan and indoor blower operation
8. Electrical voltage and operating current
9. Breakers, disconnects, wiring and terminals
10. Compressor and inverter operation
11. Refrigerant pressures and temperatures
12. Superheat or subcooling where applicable
13. Refrigerant-pipe and coil leaks
14. Reversing-valve operation
15. Defrost sensors and controls
16. Electric auxiliary heat
17. Furnace operation in a dual-fuel system
18. Duct leakage and room distribution
19. Equipment capacity compared with the building load

Measurements Matter

Weak heat can result from several different problems. For example, low airflow, low refrigerant, a dirty coil and incorrect compressor operation can produce overlapping symptoms.

Diagnosis should use operating data, manufacturer specifications and confirmed measurements.

Heat Pump Diagnostic and Repair Service

Bernoulli Heating and Cooling provides heat pump diagnostic and repair service across Metro Vancouver and the Fraser Valley.

We inspect ducted, ductless, multi-zone, full-electric and dual-fuel systems.

The current diagnostic appointment charge for an existing heat pump is $135. Repair labour, refrigerant, replacement parts and additional materials are quoted separately when required.

New heat pump installation estimates are free.

Call 604-518-4438 or email heatingbernoulli@gmail.com to arrange service.

Explore heat pump installation information:

• Heat Pump Installation Guide
• Heat Pump Installation Burnaby
• Heat Pump Installation Vancouver
• Heat Pump Installation Surrey

For general maintenance guidance, review the official ENERGY STAR HVAC maintenance checklist and the Natural Resources Canada heating and cooling maintenance guide.