A situation where the usual morning ritual is disrupted due to coffee machine dispenses a significantly smaller volume of drink than usual, which can ruin the mood of any coffee lover. Instead of a full cup of aromatic elixir, you get a pitiful semblance of espresso, and the process automatically stops long before the expected time. This does not always mean a fatal breakdown of expensive equipment; often the root of the problem lies in banal settings or temporary failures in the hydraulics.
The first thing the device owner needs to do is not to panic and look for the service center number, but to carefully analyze the nature of the change in volumes. Dosing failure can manifest itself in different ways: sometimes the device stops supplying water abruptly, sometimes it just drips slowly, and in some cases only the volume of water decreases, but not the time of spillage. Understanding these nuances will help determine whether you need decalcification, grinding adjustment or serious repair of components.
In this article, we will examine in detail the main reasons for reducing the amount of coffee, from software errors to mechanical blockages in the brewing unit. You will learn how to check the pump pressure yourself, clean the valves and reset the settings to factory settings to return the device to its previous performance without extra costs.
Software settings and broken dosing parameters
The most common and easy to fix reason is accidentally changing the user's serving size settings. Modern models such as DeLonghi Magnifica, Saeco or Nivona, allow you to save individual parameters for each cooking button. One careless press of a key combination while cleaning or wiping the panel is enough to dosing parameters were rewritten to a smaller volume.
Owners should be aware that in many devices, reprogramming occurs by holding the start button at the moment when the desired amount of liquid has accumulated in the cup. If one of the household members or guests decided to “customize” the car for themselves, he could accidentally activate this mode. Check your model's manual to understand how to enter volume programming mode and increase the pump run time to the desired value.
⚠️ Attention: When reprogramming the portion volume, make sure that there is enough water in the tank, otherwise the device may record incorrect data or generate a system error.
Sometimes a failure in the electronic control module will cause the machine to "forget" the stored values and revert to minimum factory standards. In this case, a full reset helps. This usually requires holding down a combination of buttons (often the steam button and the power button at the same time) for a few seconds until the indicators light up.
If manual adjustment does not help, the problem may lie in the calibration flow meter. This sensor counts the number of pulses from passing water and tells the control unit when to stop the process. If it is dirty or malfunctioning, the readings may be incorrect and the machine will think the cup is already full when in fact only a third is filled.
Blockages in the hydraulic system and brewing unit
The second most common reason for a decrease in coffee volume is physical obstacles in the path of water. Coffee oils, fine dust from beans and scale tend to accumulate in the machine components, creating resistance to the flow of liquid. When the pump cannot overcome this resistance or the pressure sensor detects its excess, the security system forcibly stops the cooking cycle.
Particular attention should be paid to the brewing unit (bragruppe). If you haven't removed and washed this unit in a while, the coffee tablet may have been compressed so tightly that water simply cannot pass through it at the required speed. As a result, some of the water bypasses or remains in the system, and only a small fraction of the liquid enters the cup.
☑️ Diagnosis of blockages
Another critical element is idle air valve (or bypass valve). It is designed to relieve excess pressure, but if its spring-loaded mechanism is jammed due to scale, it may remain slightly open even in operating mode. In this case, part of the water that the pump should pump simply circulates within the system or is drained into the pan without reaching the coffee.
| System element | Symptom of blockage | Cleaning method | Service frequency |
|---|---|---|---|
| Brewing unit | Coffee flows in a thin stream or drops | Rinsing with warm water, removing coffee residues | Once every 1-2 weeks |
| Boiler strainer | Weak pressure, pump humming | Removal and cleaning with a soft brush | Once every 3-6 months |
| Needle valve | Unstable portion size | Blowing or careful cleaning | When problems arise |
| Water supply tubes | Air pockets, intermittent flow | Purge the system or spill hot water | As needed |
Don’t forget to also check the filter mesh at the inlet of the water intake tube from the tank. Small debris or pieces of plastic packaging could get into the tank and block the flow of water to the pump, creating a “dry running” effect and reducing the dispensed volume.
Problems with the pump and pressure in the system
The heart of any coffee machine is the pump. It is this that creates the necessary pressure of 9-15 bar for the passage of water through the compressed coffee. If pump worn out, its membrane may have lost elasticity, or carbon deposits have formed on the motor winding, which reduces power. As a result, the pump is simply not able to pump the required volume of water in the time allotted by the program.
You can diagnose a problem with the pump by sound. A working pump operates with a characteristic, even hum. If you hear an intermittent hum, whistle or crackling noise, or if the sound becomes much quieter than usual, this is a sure sign that the pump is worn out or dirty. In some cases, the pump works, but does not develop the required pressure due to wear on the internal valves.
How to check pump pressure without a pressure gauge?
If you don’t have a special pressure gauge, you can indirectly evaluate the pump’s performance by looking at the steam jet. Turn on steam mode (without milk). If the steam comes out in a powerful, dense stream with a characteristic whistle, the pump and boiler are in order. If the steam barely breathes or comes in jerks, the problem is in the pump or heating element.
It is also worth checking the condition safety valve, which is often located near the pump. Its task is to protect the system from rupture under excess pressure. If the valve is stuck in the open position or loses its seal, some of the water will be discharged back into the tank or into the drain, which will lead to a decrease in the volume of the final product.
In rare cases, the problem may be in the electrical part: oxidation of contacts on the pump terminals or unstable voltage in the network can lead to the pump not reaching full power. Check that the wires going to the pump are securely connected and make sure that the machine is connected directly to the outlet and not through an extension cord.
Influence of water quality and degree of grinding of grains
It would seem, what does water and grain have to do with it? However, the physical properties of the ingredients directly affect the hydraulic resistance. If you change your water supplier or start using water with a high content of hardness salts, the rate of scale formation in the heat exchanger and tubes increases sharply. Scale narrows the diameter of the channels, and it becomes more difficult for the pump to push water.
The grind level of the coffee is another critical factor. If you set the grind on your coffee grinder too fine, the water will encounter enormous resistance as it passes through the tablet. The machine will try to push the water, the pressure will rise to critical, and the electronics will either stop the process or release excess pressure through the bypass, reducing the final volume in the cup.
- ☕ Try increasing the grind by one notch and check if the serving size changes.
- 💧 Use filtered water or bottled water of medium salinity to reduce the risk of sediment formation.
- 🧹 Regularly decalcify with special means that match the brand of your car.
Sometimes users forget that different types of coffee have different oil content and density. Switching to a fresher roast or a different variety may require adjustments to your settings. If the coffee is too fresh (less than 2 weeks after roasting), it produces a lot of carbon dioxide, which can also affect the permeability of the tablet and the behavior of the machine.
Use a test tablet: press the coffee in a canvas (if possible) or simply observe the shape of the “puck” after use. If it is dry and crumbly, the grind is too coarse or the pressure is too low. If it is too wet and liquid, the channels may be clogged.
Malfunctions of level sensors and flow meters
The electronics of the coffee machine blindly trusts the readings of the sensors. If flow meter (flowmeter) is dirty with coffee dust or limescale, its impeller may rotate jerkily or become stuck. In this case, it sends a false signal to the processor that the required volume of water has already been supplied, although physically much less water has passed.
A similar situation may arise with the water level sensor in the tank. If the magnetic float is stuck in the up position due to dirt or oxidation, the machine may “think” that the water is running low and go into economy or emergency stop mode, stopping the supply prematurely.
To clean the flow meter at home, intensive flushing of the system under pressure (if the design allows) or the use of special solutions to remove organic deposits often helps. However, if the impeller inside the meter is physically worn out or broken, only replacing the unit will help.
⚠️ Attention: Level sensors and flow meters are delicate components. Do not try to disassemble them yourself without skills, as a violation of the seal will lead to water leakage onto the electronic board.
When you need to call a technician: complex technical breakdowns
There are a number of malfunctions that cannot be fixed at home without special equipment and skills. If after all the checks (adjustments, cleaning, water changes) the problem persists, it is likely a serious defect. For example, wear heat exchanger (boiler), inside of which fistulas or strong deposits have formed that do not allow water to pass through.
The electronic control unit (ECU) also often fails. The microcircuits responsible for timing the pump's operation can degrade due to changes in temperature and humidity. In this case, the machine may randomly change the volume of portions or operate only in certain modes.
Another hidden problem is microcracks in the silicone tubes inside the case. Under the pressure of hot steam and water, they can expand or burst, directing part of the flow into the body of the machine, and not into the cup. This may not be noticeable from the outside until you remove the top cover.
If simple methods (adjustments, cleaning the brewing unit, decalcification) do not help within 30 minutes, further disassembly on your own may void the warranty and complicate repairs.
Frequently asked questions (FAQ)
Why did the coffee machine stop dispensing coffee after decalcification?
After the decalcification procedure, particles of dissolved plaque could remain in the system, which clogged narrow channels or valves. It is also possible that you have not run enough clean water flush cycles and the acid residue is affecting the operation of the valves. Try doing 3-5 cycles of pouring hot water without coffee.
Can an old water tank filter reduce the serving size?
Yes, if the filter jug or cartridge inside the tank is very clogged, it creates additional resistance at the inlet of the pump. The pump begins to “grab” air or work with overload, which reduces the efficiency of water supply. Replace the filter or try running the car without it to check.
What if the machine only makes small coffee in the morning?
This may be related to the temperature of the beans or water. The car is cold in the morning, and the first warm-up cycle may take longer, and the remaining water in the pipes after the night may be cold. Also check to see if you have an "Eco" or energy saving mode turned on, which limits heat or power at certain times.