89-01, 89-02 and 89-03 on a Daikin Altherma all mean the same thing: the plate heat exchanger in the indoor unit has frozen. It is one of the more serious cold weather codes, because ice inside a heat exchanger can damage it.
If an 89 code appears more than once, book a heat pump repair rather than resetting it again. An engineer needs to find out why the water stopped moving fast enough to stay above freezing.
This guide covers the 89 codes and the 7H flow codes that often come before them. For every other code, see our full Daikin Altherma heat pump error codes guide.
Please read first: this guide is here to help you understand what your Daikin Altherma heat pump is telling you. Every effort has been made to keep the information accurate, but manufacturers update their manuals and codes can differ between models and software versions, so always check the official Daikin Altherma manual for changes before acting on anything here. Do not attempt anything that could be dangerous, and avoid any work that could void your warranty. If in doubt, call a qualified heat pump engineer.
What does 89-01, 89-02 or 89-03 mean on a Daikin heat pump?
All three codes mean "heat exchanger frozen" in Daikin's Altherma 3 R W Installer's Reference Guide. The plate heat exchanger is where the refrigerant passes its heat into your heating water, and the detail number after the dash tells an engineer which version of the fault was recorded.
Daikin's guide gives the description only and refers engineers to its service manual for the fix.
The 89 codes are closely linked to the 7H family, which means a water flow problem. Daikin says that if flow drops below 12 litres per minute the unit stops for a while, shows 7H-01, then resets itself, and 7H-06 is a flow problem during cooling or defrost.
Is ice on a heat pump normal?
Yes, some frost on the outdoor unit's coil is normal in cold, damp weather, and the heat pump clears it with a defrost cycle. During a defrost the fan may stop and you may see steam rising from the unit for a few minutes.
Ice on the outside coil is a different thing from an 89 code, which means the heat exchanger inside the indoor unit has frozen. Our guide to the heat pump defrost cycle explains what a healthy defrost looks like, and our page on a heat pump frozen outside unit covers heavy icing outdoors.
Why does an 89 code appear in cold weather?
An 89 code appears in cold weather because the water and refrigerant in the heat exchanger run close to freezing, so a drop in flow lets ice form quickly. Daikin's guide does not list causes for the 89 codes themselves, but its troubleshooting pages point to flow and pressure.
What Daikin's guide says about flow and pressure:
- Flow below 12 litres per minute stops the unit and raises 7H-01
- 7H-06 is a water flow problem during cooling or defrost
- For a compressor that will not start, the guide lists low water flow and low water volume, and advises opening all valves, cleaning the filter, purging air and keeping pressure above 1 bar
Other causes (general engineering knowledge, not from the manual):
- Low flow from sludge, scale, a blocked filter or air locks
- Low system pressure from a leak or a failing expansion vessel
- Antifreeze protection settings that need checking
- A frozen or blocked condensate drain, so meltwater refreezes under the outdoor unit
- Snow, leaves or debris blocking airflow through the outdoor coil
- The outdoor unit sitting too low, so snow and meltwater build up around it
- A failing defrost sensor or valve, or low refrigerant
If your pressure keeps dropping, read our guide to a heat pump losing pressure.
What can you safely check yourself?
You can safely make a few outside checks without opening either unit.
- Keep the power on. Frost protection only works with power, so do not leave the heat pump switched off at the isolator in freezing weather.
- Clear around the unit. From outside, brush snow, leaves and debris away from the sides, top and base of the outdoor unit so air can flow and meltwater can drain.
- Check the condensate drain. Make sure the drain path under the outdoor unit is clear and not frozen. If it is iced, thaw it only with lukewarm water, never boiling.
- Check pressure and valves. Read the pressure gauge, which Daikin advises keeping above 1 bar, and make sure any heating valves you closed are open again.
- Check settings, not the switch. If you are going away, use holiday or frost settings rather than turning the system off. Our guide to heat pump holiday settings explains how.
- Restart once. Write down the full code, switch off at the breaker or isolator, wait a few minutes and switch back on. Then leave the power on. Daikin says errors should be dealt with by a licensed installer before they are reset, so do not repeat it.
What not to do:
- Never chip, scrape or prise ice off the coil, as the fins and pipes damage easily.
- Never pour boiling water or use a heat gun on the coil.
- Never remove the panels on the indoor or outdoor unit.
- Never touch the refrigerant circuit. That work is restricted to F-Gas certified engineers.
When should you call an engineer?
Call an engineer whenever an 89 code appears more than once, or if 7H codes keep showing in cold weather. Book a visit straight away if:
- The house is losing heat or hot water has stopped
- An 89 code comes back after one restart
- Water is leaking, or the pressure gauge keeps falling below 1 bar
- The indoor unit makes unusual noises or you can hear gurgling
- Ice stays on the outdoor coil for hours
An engineer will check flow, the filter, air in the system and the antifreeze protection settings. Anything involving the refrigerant circuit needs an F-Gas certified engineer by law.
How can you stop it happening again?
The best way to stop 89 codes coming back is to keep water flowing freely through the indoor unit and keep the outdoor unit clear. These steps are general engineering knowledge rather than Daikin instructions.
- Annual service. An engineer cleans the filter, checks pressure, flow and antifreeze settings, and inspects the outdoor coil. Our heat pump annual service checklist shows what is covered.
- Clean filters. A magnetic filter or strainer that is cleaned every year keeps sludge and scale from cutting flow. Badly sludged systems may need a heat pump powerflush.
- Freeze protection. Where fitted, antifreeze or freeze protection valves should be checked, and the inhibitor level kept correct.
- Insulate pipes. Insulate the refrigerant and water pipes that run outside fully.
- Raise and drain. Keep the outdoor unit on raised feet with a clear path for meltwater to drain away.
- Location. Keep the unit clear of plants, fences and drifting snow, and away from dripping gutters.
Our heat pump winter tips cover more ways to prepare before the first frost.
Other Daikin codes you might see in a cold snap
Cold weather can trigger other Daikin codes alongside or before an 89 code. Each one is explained in our Daikin error code guide.
| Code | What it means | Cold weather link |
|---|---|---|
| 7H-01 | Water flow problem | Flow below 12 litres per minute, often an early warning |
| 7H-06 | Water flow problem during cooling or defrost | Low flow while the unit is defrosting |
| A5-00 | High-pressure peak cut or freeze protection | Water flow, airflow or a frozen heat exchanger |
| E7-00 | Outdoor fan motor malfunction | Ice or debris stopping the fan |
| HJ-10 | Water pressure sensor abnormality | Low pressure cutting flow |
Need help with a frozen Daikin heat pump?
We fix frozen and iced-up Daikin heat pumps across the UK, including the Altherma 3 range. Our F-Gas certified engineers can check flow, the filter, antifreeze settings and the refrigerant side in one visit, and our repairs carry a 12-month guarantee.
If you have lost heating or hot water in a cold snap, our emergency heat pump repair team aims for same-day visits where possible. For a code that keeps returning, book a standard heat pump repair.
Regular heat pump servicing catches blocked filters and low pressure before winter, and our cover plans spread the cost. Call 0333 041 5130 or contact us online.
Frequently asked questions
Will my Daikin still heat the house with an 89 code showing?
It may stop or run in a limited way until the fault is cleared, depending on the cause. The backup heater may keep some heat going, but it costs more to run. Treat it as a stopgap and get the cause fixed.
Can a frozen heat exchanger damage my heat pump?
The code is there to protect the heat exchanger, so the unit acts before serious harm is done. Repeated freezing can still stress the heat exchanger over time, which is why an 89 code that comes back needs an engineer.
Why is my house cold in very low temperatures when there is no code?
Daikin's guide lists a backup heater that is not activated, a wrong equilibrium temperature setting, air in the system and too much capacity going to hot water. Our guide to an air source heat pump not working covers other causes.
Why does my heat pump struggle more on damp days than dry, frosty ones?
Damp air near freezing carries more moisture, so frost builds on the coil faster and the unit has to defrost more often. Our guide to running a heat pump in cold weather explains how performance changes as temperatures drop.
Why is my Daikin gurgling?
Daikin's guide links gurgling to air in the system, cleared with the unit's air purge function. It also advises checking the home screen for a refrigerant leak warning first, and if one shows, call an F-Gas engineer.
