Boilers and water heaters, Junkers
Junkersheater error codes: miniMAXX, HydroPower, Celsius and miniMAXX Excellence
Is your Junkers displaying a code on the screen and you don't know what it means? Here are all the error codes for Junkers, organized in a single table: what each one indicates, which models it appears on, and a link to the guide where we explain the causes, in order, and how to fix it.
technical troubleshooting manual Junkers for professionals and our experience as a spare parts store. It covers the miniMAXX (WR-2), HydroPower-Plus (WTD…KG), Celsius and Celsius Plus (WT…, WTD…, WTD17AM1), and miniMAXX Excellence (WTD…KME) water heaters. If you have a boiler, please consult our boiler error code index Junkers.
First of all
- The same code can mean different things depending on the model. The clearest example: the F0 code on the miniMAXX is not a circuit board fault, but rather water damage when turned on.
- Codes starting with A4, or any smell of gas or smoke: turn off the heater, ventilate the room, and don't try to fix it. Call a professional installer.
- Those that block the device (EA, E9, F7, A7, A4 in the miniMAXX) can only be removed by eliminating the cause and rearming.
- No error code is displayed? Check the guide for water heaters Junkers that won't turn on.
Junkers heater error code table
| Code | What does it mean | Models | Guide |
|---|---|---|---|
| EA | No flame detected: ignition time exceeded without flame (lack of gas, electrodes, air in the pipe) | All | EA Error |
| EC | Intermittent ionization failure (ionization probe connection) | miniMAXX Excellence | EA error (includes EC) |
| E9 | The temperature limiter has activated. Wait approximately 10 minutes before restarting | All | Error E9 |
| E1 | Overheating: the water comes out at more than about 85 °C | miniMAXX, HydroPower-Plus, Celsius Plus, miniMAXX Excellence | Error E1 and CA |
| AC | Flow rate of 30 l/min or more, out of range | HydroPower-Plus | Error E1 and CA |
| FAITH | Stepper motor disconnected | HydroPower-Plus | Error E1 and CA (includes FE) |
| A4 | Flue gas outlet: the non-return valve (AGÜ) or the gas control has been activated | miniMAXX, HydroPower-Plus | Error A4 and A3 |
| A7 | NTC probe output shorted or open | miniMAXX, HydroPower-Plus, Celsius Plus, miniMAXX Excellence | NTC probes |
| E2 | NTC inlet probe | HydroPower-Plus, miniMAXX Excellence | NTC probes |
| A9 | Incorrectly installed probe or very low inlet water pressure | Celsius Plus, miniMAXX Excellence | NTC probes |
| F7 | Detects flame even when the device is switched off or after the demand has been cut off | All | F7 and FA error |
| FA | It continues to detect a flame after the gas is turned off | HydroPower-Plus, Celsius Plus, miniMAXX Excellence | F7 and FA error |
| C2 | Pressure switch that opens when the appliance is running | Celsius Plus, miniMAXX Excellence | Pressure switch C6, C4, C2 |
| C4 | Pressure switch or flow sensor that does not open | Celsius Plus, miniMAXX Excellence | Pressure switch C6, C4, C2 |
| C6 | Pressure switch not closing (gas outlet, connections) | Celsius Plus, miniMAXX Excellence | Pressure switch C6, C4, C2 |
| F0 | miniMAXX: Water passage detected upon power-up (not the board) | miniMAXX | License plate codes |
| E0 | Internal circuit board or electronic control unit error | miniMAXX, HydroPower-Plus, Celsius Plus, miniMAXX Excellence | License plate codes |
| FC | Keys pressed for more than 30 seconds | HydroPower-Plus | Fd, FC and UU |
Codes by model
miniMAXX (WR-2)
The following codes block the heater: E9 (limiter), EA (no flame detected for 10 seconds), F7 (flame after power cutoff or circuit board failure), A7 (NTC), and A4 (anti-backflow sensor). Additionally: F0 (water flow upon ignition), E1 (temperature above 85°C), and E0 (internal circuit board error).
The manual also covers common, non-code-related problems: slow ignition or a flashing LED due to insufficient water flow, a weak flame caused by the gas cylinder regulator or cold butane in winter, or incorrect temperature due to poor contact between the sensor and the heating element. We address these in the article " water heater Junkers that won't turn on."
HydroPower-Plus (WTD…KG)
A4, A7, CA, E0, E1, E2, E9, EA, F7, FA, FC, and FE. For FA, the manufacturer recommends directly contacting a certified technician, as well as if the heater shows no indication or if the solar mode indicator is flashing.
Celsius and Celsius Plus (WTD17AM1)
They operate with a fault LED in addition to the code: F7, FA, and E0 when the appliance is locked; A7 when the LED is on; C4 and C6 when it doesn't turn on (flow sensor or pressure switch); E9 when the LED is flashing; EA when there is a spark but it doesn't ignite; C2 and E1 when it shuts down and locks out; and A9 when it flashes but is not locked. It only restarts after the cause has been eliminated and the reset button has been pressed.
miniMAXX Excellence (WTD…KME)
A7, A9, C2, C4, C6, E0, E1, E2, E9, EA, EC, F7 and FA. It is the only heater in the manual with the code EC, an intermittent ionization failure.
The three most common causes we see in heaters
- Water: low flow, dirty tap filters, or limescale in the coil. Behind many E1 and E9 errors and ignition failures.
- Ignition: Dirty or worn electrodes and faulty cables. Behind most EAs.
- Smoke evacuation: chimney, extractor hood, or lack of ventilation. Behind the A4 and many C6 models.
If your water heater simply isn't heating enough, and you don't have a code, our guide on why your water heater isn't heating the water.
Junkers water heater spare parts
- Electrode and spark plug assembly for WTD heaters and ZW boilers (87181070500)
- Ignition electrodes for WTD12-15 heaters (87387032280)
- WTD18 AME ionization sensor electrode (87387032270)
- Pressure switch for Celsius Plus and miniMAXX WTD (8738709732)
- Turbine flow sensor for WTD heaters (87070028510)
- Electronic module for WTD heaters (8738714938)
You can find all the parts you need in our water heater spares section and on the spare parts Junkers page . Always check the part number of your old part or the rating plate of your water heater before ordering.
Frequently Asked Questions
Where is the model number for my Junkerswater heater?
On the nameplate, usually on the side or bottom of the casing (sometimes you have to remove the front panel). Look for a reference that starts with WR, WRD, WTD, or WT.
Can I reassemble the heater myself?
Yes, once or twice. If the code returns, you need to find the cause. And if you get an A4 or any gas smell, don't reset it: ventilate and call a gas fitter.
My water heater uses butane. Does that make a difference?
The codes are the same, but in winter the butane may not evaporate properly, resulting in a weak flame or the flame going out. It's always a good idea to check the regulator and the date on the hose.
Important notice
This article is a guide based on the manufacturer's technical documentation and our experience as a spare parts store. It is not a substitute for professional diagnosis. Every appliance and every installation is different, and the same error code can have different causes.
Any work on the gas circuit, combustion, or flue system must be carried out by a qualified installer, in accordance with the Technical Regulation for the Distribution and Use of Gaseous Fuels (RD 919/2006) and the Regulation on Thermal Installations in Buildings (RITE). Manipulating these elements without the necessary qualifications can be dangerous and will void the appliance's warranty.
The decision to purchase a replacement part based on this information is the sole responsibility of the customer. ElectroCholo is not liable for incorrect diagnoses or damage resulting from improper installation. Electrical and electronic parts that have been assembled or installed are non-returnable if the fault turns out to be something else, in accordance with our general terms and conditions.
