Why Is My Heat Pump Blowing Cold Air?
A simple troubleshooting guide for New Zealand homeowners with high-wall heat pumps that are not heating properly, blowing cool air, or not responding as expected.
Quick Answer
If your heat pump is blowing cold air when you expect heat, first check the remote is set to heating mode, not cooling, dry or fan mode. Look for the sun symbol, set the temperature higher than the room temperature, point the remote at the indoor unit, and listen for the beep.
Then give the unit 5–10 minutes to respond. Heat pumps do not always start blowing warm air instantly, especially after changing modes or during cold weather.
What you’ll learn
- How to check the correct mode
- What the sun and snowflake icons mean
- Why the remote may not be sending the signal
- Why you need to wait after changing modes
- What defrost mode is
- When to check filters
- How to reset the system safely
- What to record before calling a technician
Before you panic
A heat pump blowing cold air does not always mean it is broken. In many cases the issue is the remote mode, flat batteries, dirty filters, defrost mode, or the unit simply needing a few minutes to change cycle.
Quick Checks First
| Check the mode | Heating mode is usually the sun symbol. Cooling is usually the snowflake. |
| Check the temperature | Set the heat pump higher than the current room temperature, such as 22–24°C for testing. |
| Check the remote signal | Point the remote at the indoor unit and listen for the beep. |
| Wait 5–10 minutes | After changing modes, the heat pump needs time to reverse cycle and start heating. |
| Check the filters | Blocked filters reduce airflow and performance. |
| Cold day? | The unit may be in defrost mode. Leave it running for 5–10 minutes so it can finish clearing frost from the outdoor unit. |
Make Sure It Is Actually in Heating Mode
This is one of the most common things we see. The heat pump may be working fine, but the remote is set to the wrong mode.
For heating, look for the sun symbol on the remote. If the remote is set to cooling mode, dry mode, dehumidify mode or fan mode, the heat pump will not blow warm air the way you expect.
It is also possible to have the heat pump set to cooling mode at a high temperature, such as 26°C. That can be confusing because the number looks warm, but the unit is still in cooling mode and may not operate the way you expect in winter.
| Icon / mode | What it means | For heating? |
|---|---|---|
| ☀️ Sun | Heating mode | Yes |
| ❄️ Snowflake | Cooling mode | No |
| 💧 Dry / dehumidify | Moisture removal | No |
| 🌀 Fan | Fan only, no heating or cooling cycle | No |
| Auto | Unit decides based on room conditions | Can be confusing |
Check the Remote Batteries and Signal
Another common issue is the remote. The customer changes the mode or temperature on the remote, but the indoor unit never actually receives the command.
Start by replacing the batteries in the remote. Then point the remote directly at the indoor unit, just like you would with a TV remote. When the indoor unit receives the command, you should usually hear a beep.
If you do not hear the beep, the indoor unit may not have received the signal. Try fresh batteries, stand closer to the unit, point the remote directly at it and press the button again.
Set It Correctly, Then Wait 5–10 Minutes
This is especially important for people who find the remote overwhelming. It is easy to start pressing buttons, changing modes and adjusting temperatures before the heat pump has had time to respond.
After changing from cooling to heating or vice versa, the heat pump needs time to reverse the refrigeration cycle. It may not start blowing warm air immediately. In some cases it can take around 5–10 minutes before you feel proper warm air from the indoor unit.
The best approach is simple: set the remote to heating mode, set the temperature to around 22–24°C for testing, point the remote at the unit, listen for the beep, then leave it alone for a few minutes.
Check the Indoor Filters
Dirty filters can restrict airflow and reduce how well the heat pump heats or cools. If the filters are badly blocked, the indoor unit may still run, but the airflow can feel weak or the room may not warm up properly.
Open the front cover of the indoor unit and check the filters. If they are dusty, remove them carefully and clean them according to the manufacturer’s instructions. Most basic filters can be vacuumed or rinsed and dried before refitting.
What Is a Heat Pump Defrost Cycle?
On cold, damp or frosty days, moisture in the outside air can freeze onto the outdoor coil of your heat pump. This is normal winter behaviour. If too much frost builds up, the outdoor unit cannot absorb heat properly, so the heat pump automatically starts a defrost cycle to clear the ice.
During defrost, the heat pump briefly reverses its refrigeration cycle. Instead of sending heat into your home, it sends heat to the outdoor coil to melt the frost. While this is happening, the indoor unit may stop blowing warm air, the airflow may feel cooler than normal, or the indoor fan may slow down or pause.
Outside, the outdoor fan may stop, steam may rise from the outdoor unit, and water may drip underneath as the ice melts. This can look alarming, but it is usually just the heat pump clearing frost from the outdoor coil.
Will my heat pump show when it is defrosting?
Many heat pumps indicate that they are in a defrost cycle by flashing or illuminating a light on the indoor unit.
Because every manufacturer is different, there is no single indicator used across all heat pumps. If you are unsure, check the user manual for your particular make and model to see whether your unit has a defrost indicator and what it looks like.
How do I know if it’s normal or a fault?
Most defrost cycles are completely normal and show that your heat pump is protecting itself from ice build-up. The guide below can help you tell the difference.
• Steam may rise from the outdoor unit
• Outdoor fan may stop temporarily
• Indoor airflow may feel cool or stop briefly
• Warm air returns once the cycle finishes
• Outdoor unit stays covered in thick ice
• Heat pump never returns to heating
• Defrost starts every few minutes
• Flashing lights or fault codes appear
What noises are normal during defrost?
During a defrost cycle you may hear whooshing, hissing, gurgling, clicking, or refrigerant moving through the system. You may also hear a large whoosh from the indoor unit as the system changes cycle. These noises are usually caused by the heat pump changing pressure and reversing the refrigerant flow.
How long should defrost take?
Most defrost cycles only last around 5–10 minutes. In very cold or damp weather, the unit may defrost more often, sometimes around once an hour depending on the conditions, location of the outdoor unit, and how hard the system is working.
After 10 Minutes, Check the Outdoor Unit
If you have set the heat pump correctly and waited around 10 minutes, it can be useful to look outside and check whether the outdoor unit is operating.
The outdoor fan may not run every single second, but if the heat pump is calling for heating and nothing appears to be happening outside after a reasonable wait, that information is useful for a technician.
Do not remove covers or put your hands near the fan. Just safely observe whether the outdoor unit appears to be running, whether the fan is turning, and whether you can hear the unit operating.
Try a Full Power Reset
Sometimes the indoor and outdoor units can have a communication error or internal fault that clears with a proper power reset.
Before calling a technician, you can try turning the outdoor isolator off to the heat pump. Leave it off for a good 5–10 minutes so the power can discharge completely. Then turn it back on, set the heat pump to heating mode and test it again.
Look for Flashing Lights or Fault Codes
If the heat pump still will not heat after the basic checks and a full power reset, look at the indoor unit for flashing lights.
Many heat pumps use flashing lights to display fault codes. The lights often blink in a sequence, pause, and then repeat the same sequence again.
If you can, take a clear video showing the full pattern from start to finish. Make sure the video captures the complete sequence, including the pause and repeat. Sending this along with the Make and model number of your heat pump to your technician can help them diagnose the fault more quickly.
What If It Is Not Cooling in Summer?
Many of the same checks apply in summer, but in reverse. If the heat pump is not cooling, first check that the remote is set to cooling mode, usually shown by the snowflake symbol.
Set the temperature lower than the room temperature, such as 18–20°C for testing, point the remote at the unit, listen for the beep and wait a few minutes for the system to respond.
Also check the filters. Dirty filters reduce airflow and can make the system perform poorly in both heating and cooling.
When Should You Call a Technician?
If you have checked the mode, remote batteries, signal, filters, outdoor unit operation, defrost behaviour and completed a safe power reset, but the heat pump still will not heat or cool properly, there may be a more serious fault.
At that point, it is best to have the system checked by a qualified technician. There could be an issue with communication between the indoor and outdoor units, sensors, fan motors, refrigerant circuit, compressor operation or another internal fault.
If you can, take a short video of any flashing lights, unusual sounds or behaviour before calling. That information can make diagnosis much easier. Sending through the Make and Model and Serial number information located on the outdoor Nameplate is also helpful for diagnosing a repair and age of unit.
Frequently Asked Questions
Why is my heat pump blowing cold air in heating mode?
It may be in defrost mode, changing cycle, set incorrectly, restricted by dirty filters, or it may have a fault. Start with the simple checks in this guide.
How long should I wait after switching to heat?
Give the heat pump around 5–10 minutes after changing modes. It may need time to reverse cycle before warm air starts.
What symbol is heating mode?
Heating mode is usually the sun symbol. Cooling mode is usually the snowflake symbol.
Why does my heat pump make a whoosh sound?
A whoosh sound can happen when the unit changes cycle or enters defrost mode. This can be normal, especially in winter.
Why is the outdoor unit steaming?
Steam from the outdoor unit can be normal during defrost mode. It often looks alarming, but it can simply be the unit clearing frost.
Should I turn the heat pump off at the isolator?
A safe power reset can sometimes help clear communication errors. Turn the outdoor isolator off, wait 5–10 minutes, then turn it back on. Only do this if the isolator is safe and easy to access.
Related Guides
To keep this guide focused, these related questions are best covered in their own articles.
Still not getting warm air?
If the simple checks do not solve it, we can inspect the unit, check for fault codes and diagnose the issue properly.