What it means
Daikin's Altherma 3 R ECH2O guide lists 89-02 (freeze protection during heating or hot water) and 89-03 (during defrost) as warnings, and 89-01 as the error during defrost. Daikin's service manual says 89-01 appears when one of those warnings happens 3 times with less than 30 minutes between them, and that 89-01 has to be reset at the controller. The Altherma 3 R W guide simply calls all three "Heat exchanger frozen".
What to check, in order
- Check the water pressure
Low water pressure and low water flow are among the causes in Daikin's service manual. Daikin's user guides say the pressure should be above 1 bar.
- Read the help text
On the controller, open the main menu and choose Malfunctioning to see the code and a short description. The help button gives a longer one. Note the code for your installer.
- Use emergency heating if you need it
Daikin's user reference guide says the backup heater can take over the heating when the heat pump fails. If emergency mode is set to Manual, you confirm this on the Malfunctioning screen. Expect higher electricity bills while it runs.
When to call your installer
Call your installer before resetting it, because Daikin wants the cause found first. Its service manual lists low water flow or pressure, faulty water or refrigerant thermistors, a faulty hydro PCB, a closed refrigerant stop valve, a blocked refrigerant circuit, too much refrigerant, or air or moisture in the refrigerant circuit. Refrigerant work needs an F-gas certified engineer.
A repair visit will usually check the water flow and pressure, the temperature sensors and the refrigerant circuit.
- Note the model and serial number. They're on a label on the rating plate on the outdoor unit, and on the indoor unit or cylinder.
- Write down the exact code, and what the appliance was doing when it appeared.
- Check whether it's still under warranty. If it is, the repair may cost you nothing.
Quick answers
What does the Daikin Altherma 89-01 error code mean?
The heat pump's freeze protection has been triggered several times in a short period, so it has shut down to protect the water heat exchanger from freezing. Daikin's Altherma 3 R ECH2O guide lists 89-02 (freeze protection during heating or hot water) and 89-03 (during defrost) as warnings, and 89-01 as the error during defrost. Daikin's service manual says 89-01 appears when one of those warnings happens 3 times with less than 30 minutes between them, and that 89-01 has to be reset at the controller. The Altherma 3 R W guide simply calls all three "Heat exchanger frozen".
Can I fix Daikin Altherma 89-01 myself?
Tricky (engineer visit likely). Start with: check the water pressure; read the help text; use emergency heating if you need it. Call your installer before resetting it, because Daikin wants the cause found first. Its service manual lists low water flow or pressure, faulty water or refrigerant thermistors, a faulty hydro PCB, a closed refrigerant stop valve, a blocked refrigerant circuit, too much refrigerant, or air or moisture in the refrigerant circuit. Refrigerant work needs an F-gas certified engineer.
Is Daikin Altherma 89-01 worth repairing?
Worth fixing. Worth fixing promptly: repeated freeze trips point to a flow, pressure, sensor or refrigerant problem that needs diagnosing.
Checked against
- Daikin Altherma 3 R W installer reference guide 4P496758-1B, error codes, p. 90 (ManualsLib copy)
- Daikin Altherma 3 R ECH2O installer reference guide, error codes overview, p. 274 (ManualsLib copy)
- Daikin service manual ESIE20-06A, Daikin Altherma 3 M (EBLA/EDLA), PDF (copy hosted on the OpenEnergyMonitor forum)
- Daikin Altherma low temperature split user reference guide 4P499574-1A (EHVH04/08S23DAV), PDF
- Daikin Altherma 3 R ECH2O installer reference guide, AH error and help text, p. 273 (ManualsLib copy)
Last reviewed October 2026. Manufacturers update their pages, and your manual is the final word. Spotted a mistake? Email contact@appliance-error-codes.com.