Junkers gas boiler malfunctions: error codes and how to fix them

A boiler breakdown at the height of the heating season is a nightmare for every owner of this equipment, isn't it? Have you ever had the boiler stopped, the house is cold, and the master can only come in a few days? Such malfunctions of the Junkers gas boiler can be desperate.

Do not rush to panic, because many breakdowns of gas boilers can be eliminated on your own, without experience and special tools, and we will teach you this.

In this article, we will not only give a decryption of the error codes that the boiler issues, but also link them to the current state of the unit. We will also tell you how to fix some malfunctions and in which cases you cannot do without the help of a specialist.

The gas boiler does not turn on

When the boiler is not working and not a single light is on, it does not react to the power button in any way, the owner is overcome the most terrible suspicions: the unit is hopelessly broken, serious repairs or the installation of a new one will be needed equipment.

The boiler self-diagnosis function is powerless here and the device will not issue an error code.

Often the reason is simple: the plug is pulled out of the socket, or the machine is turned off. The plug could be pulled out by the child while playing, and the machine could turn off to protect against network outages. In addition, there may be no power supply throughout the house - during the day it can easily be overlooked.

If everything is fine with the power supply, and the boiler is still silent, disconnect it from the mains and remove the front cover. The control panel in wall-mounted models is usually secured with two screws, and the main compartment cover is screwed in the corners - a Phillips screwdriver is enough to remove them.

The problem may be a blown fuse on the control board, while boilers of the series EuroStar may issue error E9. Find it and inspect, if possible, check with an ammeter. If you need to replace the fuse, look for a spare on the inside of the lid or other elements of the boiler drum. As a rule, Junkers makes such a stock for the user.

After checking the marking, replace the fuse and try to start the boiler without directly assembling. If everything worked, you can breathe a sigh of relief, but if there is no reaction or the new fuse burned out immediately, you need to call a specialist.

Inspect the interior of the machine for traces of short circuits, leaks, broken or pulled wires.

The varistor on the board may be exploded or damaged - this indicates that there was a power surge. The repair is not too complicated and expensive, but it requires soldering the board, and we strongly do not recommend doing this on your own. Entrust the work to the master, and buy a voltage stabilizer yourself.

It happens that the boiler does not start working even when it is cold in the house. At the same time, the standby mode can be displayed on the display or indicators, and on EuroStar models - SS error. This indicates that there is no communication with the room temperature sensor or the boiler thermostat. Check the integrity of the wires and connections, tighten the contacts. If everything is intact, turn the knob on the mechanical sensor, and replace the battery on the electronic one.

If a piezo ignition boiler tries to light the burner, gives a spark, but does not ignite - most likely, there is no gas supply or is faulty gas valve.

After several unsuccessful attempts to start the ruler model Ceraclass and Eurostar highlight EA error “Flame not detected”, the “reset” button and the temperature indicator 60 flash on the Euroline.

In such a situation, you can only try to light the stove or unscrew the gas hose of the boiler (with the tap closed and the boiler turned off) and try to open the gas for a while. If a hiss is heard or the stove turns on - the problem is in the boiler, you need to call specialists from the service department with which you are maintenance contract gas equipment.

If there is no hiss, then the gas supply to the house is turned off, wait until the gas supply is restored. In any case, the unscrewed gas hose must be connected back to the boiler without losing the gasket.

The boiler is constantly shutting down

One of the most common problems: the boiler starts up, the burner ignites and then shuts down. At the same time, it can issue error E9, CE, EA or the lamp is flashing 45 or 75 degrees - "no ionization current".

Such a problem can occur every time when firing up or occasionally, unpredictably, instantly or after a short period of time - because the reasons for this behavior of the boiler can be different. We will talk about possible problems and their solutions further.

Reason # 1 - the filter is clogged

This is a common malfunction. double-circuit boilers, which is rarely indicated by self-diagnostics, because the water supply filter is usually located outside and is not connected to the sensor.

Disconnection occurs when you try to switch to hot water supply, because water does not flow into the coil or it flows with a weak pressure and the boiler overheats.

To clean the filter, turn off the boiler and locate an inverted U-shaped section on the boiler water supply pipe.

Before and after it, turn off the taps, unscrew the nut - the tip. Remove and rinse the mesh thoroughly, rinse the case. If the cartridge is damaged - bent or burst, then buy a new one. Collect everything back and open both taps.

Reason # 2 - pump jammed

In most models of Junkers gas boilers, the pump is built-in and controlled by the system, its malfunction is indicated by a flashing 45 degree diode, error E9, depending on the model.

To find out if the pump rotor is jammed, it must be disassembled.

To do this, follow these steps:

• turn off the boiler;
• find the pump in the lower right part of the boiler;
• place a small container under it;
• to remove the cover, unscrew the screw with a large shiny head for a flat screwdriver;
• a little water will drain from the pump - make sure that it does not get on the printed circuit board and other electronics;
• try turning the rotor slightly at the back of the pump with the tip of a screwdriver. If it goes easily, we collect and look for a malfunction further, if not, we repair or change the pump;
• reassemble everything in reverse order.

A more risky, but also more accurate way of checking is to turn on the boiler with a disassembled pump and covered with water and gently push the screwdriver deep into the the rotor.

If the pump is clogged with air that has entered the heating system, a special valve will help to release it.

Depending on the design, it can be unscrewed or lifted. When the coolant supply valve is open, the air will come out with a hiss, and the boiler will work as before.

Reason # 3 - sensor is faulty

It happens that the main burner has time to ignite, but it immediately goes out and the boiler gives out EA error or the diode is flashing 60 degrees. This means that it does not work correctly. flame control sensor - thermocouple or ionizer diode and the protection is mistakenly triggered, turning off the burner in order to avoid gas leakage without burning.

To fix such a malfunction, it is not always necessary to change the sensor, sometimes it is enough to unplug the boiler from the socket and insert it upside down. This manipulation helps because many Junkers boilers are phase-dependent, if the phase and zero of the boiler and the outlet do not match, the ionization current does not form and the sensor does not work.

Another reason for such a breakdown is a zero and ground circuit in any part of the electrical wiring in the house. Remember, have you recently hammered in nails, have not connected a new electrician? All equipment works with such a short circuit, only grounding is incorrect.

If a similar problem is found, eliminate it and restart the boiler.

In all the cases described above, the boiler was turned off immediately, it could not enter the operating mode even for a short time.

If the device as a whole works, but sometimes, at different intervals, more often from several hours and days - rises by mistake EA "flame is not detected", then the reason is, most likely, low-quality and unstable voltage in networks.

This situation is not only annoying, but also threatens to break the board. To prevent this, purchase a voltage stabilizer.

Low coolant pressure

On the front panel of each boiler there is a pressure gauge indicating heating system pressure. It has red zones of too low and too high readings. A pressure of 1.5 bar is considered normal for a cold boiler: at 1 bar, the arrow is already in the red zone, and at 0.5 bar, the boiler will turn off by CE error or CF until the pressure is restored.

If the boiler was installed recently - a few weeks ago, this situation is common, you just need to top up with clean water through a special tap. But do not rush to add water to the system, which has been in operation for several years.

As the water heats up, it expands and the pressure rises - this is the norm. However, if it jumps immediately to 0.7 - 1.5 bar, this indicates a lack of air in the expansion vessel.

If, in such a situation, water is added while heating up, it will increase the pressure too much and the safety valve will work, dumping the excess coolant.

To pump up the tank, you first need to relieve the pressure on the disconnected boiler by draining a little water. Then connect the pump or compressor to the union at the upper rear of the tank and inflate it to 1.3 - 1.4 bar. After turning off the pump, add water, bringing the pressure in the cold system to 1.5 - 1.6.

If even when the boiler heats up, the low pressure in the heating circuit persists, then it is really necessary to add water. Where to find the tube intended for this is indicated in the instructions for the device model, we only recall the need to fill this tube with water before opening the tap so that air does not enter the pump and batteries.

Be sure to check all taps, connections and radiators, as well as the inside of the boiler for leaks - the water circulating in the system has gone somewhere.

No draft in the chimney

Draft problems are also familiar to all types of boilers - both with a conventional chimney and with a coaxial one. Indicate this problem errors A4, C4, C6, the flashing of the diode is 45 degrees, sometimes - alternately from 90 degrees.

When such errors occur, first of all, you need to find out if there really is a problem, because thrust sensor could have tripped erroneously, and C4 and C6 failures may also indicate a problem with the pressure switch.

To check the draft, first find out where your boiler is taking combustion air from. Models with an open combustion chamber take it from the room, as a rule - through the grate at the bottom of the wall-mounted and on the side of the floor-mounted versions. With a closed combustion chamber, air is taken from the street through the outer pipe of the coaxial chimney.

Hold a piece of paper near the air intake point when the equipment is running or trying to operate. If it sticks to the grate or is pulled into the pipe, then everything is fine with the draft.

If there is a pull, but weak, it may not be enough to hold the paper. In this case, a burning match is used for verification.

Open chamber boiler

Most often, when traction errors appear, it really is not. The main reason is chimney problems. He might be:

• clogged with soot or acid condensation;
• clogged with foreign bodies - sometimes birds can twist a nest in the chimney, the remains of which will fall inside;
• incorrectly calculated - too thin or short;
• not insulated enough, an airlock has formed.

Inspect and clean the pipe, if necessary, use the services of specialists.

Turbocharged gas boiler

A fan is responsible for air exchange in boilers with a closed combustion chamber, controlled by a flue gas pressure switch - a pressure switch.

Traction failure is usually caused by a malfunction of one of these devices.

The owner of the boiler himself can check the integrity of the inductance coil with a multimeter - it must have a resistance of 50 - 80 Ohm, otherwise it must be replaced. Also, due to the accumulation of dirt and dust, the fan impeller can be unbalanced.

To find this out, remove the turbine, blow out the dust and turn the impeller several times. If it always stops in one position, attach a weight to the upper blade and check again.

In addition, the pressure switch may not start the fan due to low voltage in the network: check it with a voltmeter in the outlet, the lower limit of the allowable is 195 V. If this is the problem, connect the stabilizer.

To check the performance of the pressure switch, connect the fan directly and try to start the boiler. If the problems in operation have disappeared, the pressure switch needs to be replaced.

Boilers with a closed chamber are supplied with coaxial chimneys, which are installed horizontally, and therefore are practically not subject to clogging. However, in severe frost, icing of the pipe end may occur due to freezing of condensate or improper installation of equipment.

You can get rid of this problem by insulating the chimney.

Other malfunctions and code meanings

Most of the error codes that we have not yet mentioned indicate a distress signal from a specific sensor, caused by its breakdown, a broken line, or a malfunction of the controlled equipment.

You can find out all the error options that the Junkers wall-mounted gas boiler produces and repair it in the instructions for your model. Depending on the series, indication method and boiler configuration, the list of errors may differ, and sometimes the same code in different models does not have a completely identical meaning. Therefore, we will not give a complete list here so as not to confuse you.

Malfunction # 1 - noise during operation

The boiler drum is not hermetically sealed and dust often accumulates in it. Most of all it accumulates on the fan impeller, because it sucks dirty air out of the boiler.

If you have an air compressor, the problem is easy to fix. Remove the front panel of the boiler and unscrew the turbine. Blow out the entire fan with compressed air, then the place of its seat, and then the entire boiler. Be careful when cleaning the board - the blast of air can knock out the contacts.

Let the dust settle in the room and repeat the boiler blowdown. Do several of these cycles until complete cleaning.

The impeller and fan housing can be cleaned with soapy water - just do not get the motor and electrical contacts wet. If there was a lot of dust, ask the Junkers gas boiler service and repair specialist to remove and flush the gas burner as well. You should not do this yourself - incorrect installation threatens with gas leakage and explosion.

Fault # 2 - batteries do not heat up

If the double-circuit boiler does not switch to heating mode, even when all hot water taps in the kitchen and bathroom are closed, the flow sensor is most likely faulty or three-way valve. In this case, the error, as a rule, is not displayed - it seems to the boiler that there is a constant water intake, and it works in accordance with this situation.

If you have been using hot water for a really long time and the batteries have cooled down, the boiler is operating normally, the DHW circuit has priority.

When this problem occurs already at the first start after installation, design errors are possible. For example, a heated towel rail can be connected to the DHW circuit, as in high-rise buildings with centralized hot water supply.

Water constantly circulates in it, and therefore the flow sensor does not close and does not allow the boiler to start heating.

Malfunction # 3 - Board Errors

The electronic control board is the most capricious and expensive part of a modern boiler, its error F0, E0 or a flashing 75 degree indicator can seriously upset the owner who has looked into the instructions for decoding.

However, everything is not always so bad: it is possible that the contacts have simply come off, and on the Cerapur series boilers, it also indicates the wrong ratio of gas and air supplied to the burner. Moisture on the circuit board may also be the cause of the problem. Everything will work after thorough drying.

It has been experimentally established that sometimes the errors of the board are eliminated by themselves if you set the 5th fan operating mode.

In addition, sometimes the board does not work correctly, the boiler behaves strangely, but does not give an error. Poor quality of electricity can be the reason for this. Try to disconnect the boiler from the mains for half an hour so that all capacitors are discharged, and then start again. If it helped, that's the problem. Factory reset may also help.

The specialist can also re-solder or reflash the board, restoring its performance.

Conclusions and useful video on the topic

You can more clearly get acquainted with the most common breakdowns of Junkers boilers and their self-repair in the video.

Troubleshooting the flow sensor:

DIY Junkers boiler repair:

As a conclusion, we can note that not every error generated by the boiler self-control is fatal. Do not be afraid of self-repairing the Junkers boiler: many faults can be eliminated without the help of a specialist. But we do not recommend interfering with the gas pipeline yourself and soldering the board, this is too risky.

Did your Junkers boiler stop by mistake? Did you manage to solve the problem on your own or did you have to resort to the help of specialists? Tell our readers about it - join the discussion in the comments.