What a few minutes of checks can settle
A fully automatic coffee machine is a set of sensors watching a set of containers. Water in the tank, beans in the hopper, a drip tray in place, a grounds container emptied, a door closed: if any one of them reads wrong, the machine refuses to brew, and from the outside a refusal looks exactly like a breakdown.
The checks below go in the order the machine itself goes through when you press a button. Work from the top, stop at the first thing you find, and try a drink after each fix.
Power, the switch and the breaker
A dark display is not always a dead machine. Miele asks for its on button to be held for at least three seconds and lists a plug that has worked loose and a tripped breaker among the causes. Bosch's built-in has a separate power switch as well as the controls on the panel, and a clock showing 12:00 means it lost power and needs its settings entered again.
If the machine reports a voltage that is too high or too low, Bosch sends you to the power company and a qualified person to check the supply, not to the machine.
A breaker that trips a second time
Reset a tripped breaker once, from a dry floor. If it trips again, leave it off and book: repeated tripping points to wiring or a heater inside the housing, and neither is an owner's job.
Where the outlet of a built-in is
The plug of a built-in coffee system is usually behind the unit or in the next cabinet. Use the breaker instead of trying to reach the outlet, and never slide the machine out of its opening to get to it.
Source: Miele — CVA 6405 built-in coffee system, operating and installation instructions — Hold the on button at least 3 seconds; loose plug or tripped fuse; door will not close when containers are not pushed in; soiled drip tray contacts give a false empty-tray message; grease the main dispenser cap at least once a month; never open the casing; Bosch — BCM8450UC built-in coffee machine, use and care manual — 12:00 on the display after a power failure; overvoltage or undervoltage message, have the supply checked; drip tray emptying is not detected when the appliance is off; wait a few seconds before removing the tray; water under the drip tray is condensation
Water, beans and the two trays
These are the sensors that stop drinks most often. Each check takes seconds, and each one is described in the maker's own troubleshooting pages.
- Tank: lift it out, check the float moves, fill with still cold water, push it home until it seats.
- Water valve on a plumbed unit: the shutoff under the sink fully open.
- Beans: hopper at least a third full, with no oily beans stuck to the walls above the grinder.
- Drip tray: emptied, wiped dry, pushed all the way in.
- Grounds container: emptied and pushed fully home behind the drip tray.
- Door: closed firmly on a built-in; Miele notes it will not close if a container is out of place.
A tray message that stays after emptying
Miele traces an empty-the-drip-tray message on an empty tray to soiled contacts and asks for them to be cleaned and dried. Bosch adds a less obvious rule: empty the tray while the machine is switched on, or it does not register that you did, and take the tray out only a few seconds after the last drink. A little water under the tray on a Bosch is condensation and is normal.
Source: Miele — CVA 6405 built-in coffee system, operating and installation instructions — Hold the on button at least 3 seconds; loose plug or tripped fuse; door will not close when containers are not pushed in; soiled drip tray contacts give a false empty-tray message; grease the main dispenser cap at least once a month; never open the casing
The door, the brew unit and the spout
On makes with a removable brew unit, switch the machine off, let it cool and take the unit out exactly as the manual shows. Rinse it, let it dry and refit it. Miele also asks for the silicone cap on its main dispenser connector to be greased at least once a month, because a dry cap makes the door hard to open and close.
Look at the spout while you are there. Dried coffee or milk on the outlet parts changes the flow long before anything inside the machine does.
Source: Miele — CVA 6405 built-in coffee system, operating and installation instructions — Hold the on button at least 3 seconds; loose plug or tripped fuse; door will not close when containers are not pushed in; soiled drip tray contacts give a false empty-tray message; grease the main dispenser cap at least once a month; never open the casing
One test drink, and the notes that shorten a visit
Make a single plain coffee with a cup in place and stay beside it. Listen for the grinder, the brew unit moving and the pump, and watch the flow into the cup.
Then write down what you found. A technician who arrives knowing the model, the message and the sounds brings the right parts the first time.
- Model and serial number from the data plate.
- The exact wording or code on the display, with a photo.
- When it started and what changed that day: new beans, a descale, a power cut, a move.
- Tank or water line, and whether a water filter is fitted.
- Which drinks work and which do not.
Signs that end the checks at once
Some findings are not a reason to keep going. Water spreading from the machine or its cabinet toward an outlet, a burning or hot electrical smell, a breaker that trips again, and steam or scalding water coming from anywhere other than the spouts all mean the same thing: switch the circuit off at the breaker from a dry spot, close the shutoff under the sink on a plumbed unit, keep clear and book.
