Quick answer
If your heat pump's auxiliary heat isn't working, check the thermostat settings, ensure the outdoor unit is clear of debris, and test the emergency heat function. If these steps don't resolve the issue, a faulty component may need replacement.
Confirm the symptom
- Indoor temperature is not reaching set point
- Thermostat shows auxiliary heat is on but no additional heat
- System runs continuously without warming the home
Tools and prep
- Screwdriver set
- Multimeter
- Thermostat manual
- Safety gloves
- Turn off power to the heat pump at the circuit breaker
- Clear area around outdoor unit for safety
Step-by-step troubleshooting
- Check Thermostat SettingsDo: Verify the thermostat is set to 'Heat' and the temperature is higher than the room temperature.Observe: Thermostat displays correct mode and temperature.Means: Thermostat settings are correct.Next: Proceed to step 2.
- Test Emergency HeatDo: Switch the thermostat to 'Emergency Heat' mode.Observe: Auxiliary heat engages and the system starts producing heat.Means: Auxiliary heat is functional.Next: Issue is resolved.
- Inspect Outdoor UnitDo: Check the outdoor unit for ice buildup, debris, or obstructions.Observe: Outdoor unit is clear and operational.Means: No physical blockages affecting performance.Next: Proceed to step 4.
- Check Circuit BreakerDo: Inspect the circuit breaker for the heat pump to ensure it hasn't tripped.Observe: Breaker is in the 'on' position and not tripped.Means: Power supply to the heat pump is intact.Next: Proceed to step 5.
- Test Auxiliary Heat RelayDo: Use a multimeter to test the auxiliary heat relay for continuity.Observe: Relay shows continuity when activated.Means: Relay is functioning properly.Next: Proceed to step 6.
- Inspect Heating CoilsDo: Check the heating coils for damage or wear.Observe: Coils are intact and undamaged.Means: Heating coils are operational.Next: Issue may require professional assistance.
Common causes
| Cause | Likelihood | Difficulty | Part often needed |
|---|---|---|---|
| Thermostat Misconfiguration Incorrect settings can prevent auxiliary heat from activating properly. | Common | Easy | Thermostat manual |
| Dirty or Blocked Outdoor Unit Debris or ice can restrict airflow and reduce efficiency. | Common | Easy | None |
| Tripped Circuit Breaker A tripped breaker cuts power to the heat pump components. | Sometimes | Easy | None |
| Faulty Auxiliary Heat Relay A failed relay prevents the auxiliary heat from engaging. | Sometimes | Medium | Auxiliary heat relay |
| Damaged Heating Coils Worn or broken coils cannot produce sufficient heat. | Rare | Hard | Heating coils |
| Low Refrigerant Levels Insufficient refrigerant reduces the system's ability to transfer heat. | Rare | Hard | Refrigerant charge |
Parts matching
Common parts needed for heat pump auxiliary heat repairs include:
- Thermostat manual
- Auxiliary heat relay
- Heating coils
- Refrigerant charge kit
Always refer to your heat pump's manual to ensure part compatibility before purchasing replacements.
When to call a professional
- System still doesn't produce heat after following these steps
- You detect a burning smell or unusual noises
- You're unsure about handling electrical components
- Refrigerant levels are low and require professional refilling
- Multiple components are faulty or need replacement
FAQ
What is auxiliary heat on a heat pump?
Auxiliary heat is a backup heating source that activates when the outdoor temperature is too low for the heat pump to operate efficiently or when additional heating is needed.
Can I use emergency heat all the time?
Emergency heat should only be used temporarily, as it consumes more energy and increases utility bills. Use it only when necessary, such as during extreme cold or system malfunctions.
Why is my heat pump running but not heating?
This can be due to a variety of issues, including a malfunctioning thermostat, dirty filters, low refrigerant, or a problem with the auxiliary heat system.
How often should I check my heat pump's auxiliary heat?
It's a good idea to check your heat pump's auxiliary heat system at least once a year during routine maintenance to ensure it's functioning properly.