F7 and FA error in Junkers: detects flame with the appliance switched off (what it means and what to check)

Your Junkers has locked with error code F7 or FA , and what you're reading doesn't make much sense: "detects flame with the appliance off." How can there be a flame if it's not switched on? That's precisely the key. In most cases, there's no flame at all: the hob is mistaking something for one. This could be moisture, a dirty electrode shorting to ground, or a poor ground connection. However, there is one case, the FA error, where there could be a serious problem with the gas valve, and it's important to know how to distinguish between these.

Why does the boiler "see" a flame that doesn't exist?

boilers and water heaters Junkers detect the flame by ionization: they apply a small voltage to an electrode inside the burner and measure the tiny current that passes through the flame to the ground. We explain this in detail in the guide for error code EA, which is the exact opposite problem.

The consequence is that any path that allows current to pass through resembles a flame. A drop of water connecting the electrode to the casing, moisture on the circuit board, a wire with damaged insulation touching ground, or an electrode covered in conductive dirt. The board cannot distinguish this from a real flame, so it shuts down for safety. That's why the Junkers repeats the word "moisture" in these two codes.

F7: What to check

1. Moisture on the hob or connections. Is the appliance in a damp place, on an enclosed terrace, or on the stovetop? Has there been any water leak or condensation? The F7 error code that appears mainly in the mornings or on humid days points to this.
2. Electrode and its cable. A dirty, cracked, or misaligned electrode, or a cable with cracked insulation, can divert current to ground.
3. Flue gas duct. Junkers asks on several models if the flue is in good condition. A flue with condensation dripping inwards will eventually wet the burner and electrodes.
4. Grounding and power supply. In Celsius heaters, the manual states this first: Is 220V present? Is there a good ground connection?
5. The circuit board. If everything else is working correctly and the F7 error persists, the board may be damaged. It's the last thing to check, not the first.

FA: What to check (and when it's serious)

FA is the opposite of F7: the appliance has just shut off the gas, but the hob is still showing a flame. There are two very different possibilities:

• There's no real flame: just like with the F7, it's due to humidity, the electrode, or the wiring. That's the most common problem.
• Yes, there is a real flame: the gas valve isn't closing completely and the burner is still receiving a trickle of gas. This is a safety hazard. If, when you turn it off, you see through the viewing window that the flame isn't going out, or you smell gas, turn off the gas valve on the appliance and call a qualified electrician.

In condensing boilers, there's an extra suspect: the manual instructs you to clean the condensate trap. If the trap becomes clogged, the condensate flows back towards the burner and wets the electrodes.

What does the Junkers technical manual say about the model?

Condensing boilers: Cerapur, Comfort, Excellence and Acu

F7: A flame appears even though the appliance is off. Check the electrodes, the gas duct, and ensure the electronic board is not wet. FA: A flame is still detected after the gas is disconnected. Check the gas valve, clean the condensate trap, the electrodes, and the gas duct.

Ceraclass Excellence and Cerastar

F7: Flame with the appliance switched off. Electrodes and cable, exhaust gas path, and moisture on the plate. FA: Flame continues to be detected after the gas is switched off. Ionization electrode and gas valve.

Eur(note, different meaning)

F7: Incorrect ionization signal. Check the ionization electrode and its cable (cracks, cuts) and check for moisture in the Heatronic junction box. FA: Ionization current persists after a normal shutdown. The manual recommends checking the gas body wiring.

Ceraclass Midi (note, different meaning)

F7 with reset: Incorrect ionization signal: Damaged ionization electrode and cable, or moisture. FA: Gas valve error: Check the valve wiring.

Heaters

• miniMAXX: F7 indicates the presence of a flame after the hot water demand has been cut off, or a circuit board failure. Locks the appliance.
• miniMAXX Excellence: F7, check electrodes, cable and plate; FA, gas valve and gas duct.
• HydroPower-Plus: F7, check electrodes and cable, gas duct and plate; FA, call an accredited technician.
• Celsius Plus: F7, FA or E0 with the device locked: check 220V voltage and good ground connection, that there is no ionization before switching on and, if it persists, replace the electronics.

Euronline (without screen)

Red LED with the fourth green LED: no spark and it detects a flame, i.e., a false flame signal. The manual points to the electronic board, moisture on the board, and ionization. You can find all the combinations in the light EurEuroline.

What you can do (and what you can't)

Safe: Check if the appliance is in a damp place or if anything is dripping on it, ventilate the room, check that the plug has a ground connection and observe through the peephole if the flame goes out when the power is cut off.

For the installer: dry or check the plate, change electrodes, clean the siphon, check the duct and, above all, any check of the gas valve.

Related spare parts

Electrodes:

• Electrodes for Cerapur, Cerasmart and Europur (87186649200)
• Electrodes for Cerapur Comfort ZWBC (87161163810)
• Electrodes for boilers ZWSE 23/28 (87167605510)
• ZWA24 Electrode Eur(87199051490)
• Electrodes and spark plug for WTD heaters and ZW boilers (87181070500)

Electronic boards (only when all the above has been ruled out):

• Plate for Cerastar ZWN 24 (8748300949)
• Plate for Ceraclass ZWSE (8748300950)
• Plate for ZWC 25/30 boilers (8748300923)
• Electronic module for WTD heaters (8738714938)

Always check the reference number on your rating plate. More parts are available in spares Junkers , and all error codes can be found in the error code table Junkers.

Frequently Asked Questions

Is the F7 error dangerous?

Normally not: the boiler locks itself out precisely to prevent ignition in a potentially dangerous situation. However, you should keep an eye on the FA (fire indicator light) if you see the flame won't go out or you smell gas.

I only get F7 in the mornings or when it rains. Why?

This is a typical moisture pattern: condensation on the circuit board or electrodes when the device is cold. It dries with use and the code disappears, only to reappear the next morning. We need to find the source of this moisture.

Can I dry the plate with a hairdryer?

We don't recommend attempting this without the necessary expertise: you have to disconnect the power, open the appliance, and with sealed boilers, that's a job for a professional installer. Furthermore, if the source of the dampness isn't addressed, it will return.

What's the difference with EA?

EA a flame unexpectedly.