Thursday, February 2, 2017

Automated coffee machine troubleshooting chart

My old post on the Saeco Talea Giro machine teardown (including deprecated one) has had tremendous success and I frequently get questions on how to fix this or that.

I am no specialist on this stuff but I've managed to keep my unit running after it was used in an office environment (>50000 coffees). So for me it's mostly guesswork and some logic, but I'll display this so that you can help figure out the problem with your own unit. I'll try to make this accessible to non-technical people, let me know if some idioms are too advanced.

I will try to update this guide with usual questions, but this is not a replacement for professional servicing.

Before troubleshooting make sure that the unit is cleaned and descaled and has enough water. Use the manual for this, each unit is different. Also, try turn the unit off and on, perhaps leaving it 1h undisturbed. This works around some of the bugs in software (firmware).
Learn the sounds of the machine and try to understand what it does in its normal state. There are several motors and they are easy to identify by sound.

Refer to my original post (from years ago) if you want to understand more about how such a unit is constructed:

I also plan to do a series of videos on how coffee machines work (various types), I'll link it here when it's done.

First we need to have a common language, use this as a reference, no need to read it now:

  • hopper: where the coffee beans go
  • water reservoir (tank): where the intake water goes
  • waste bin: spent water (wastewater) and coffee grounds (spent coffee) goes there, usually separate from each other
  • grinder: sits below the hopper and grinds coffee with a ceramic wheel
  • brew group (assy for short): the rotating arrangement that moves ground coffee around, from the grinder, to the water/steam pipes, to the waste bin. Do not machine wash! (because of the low-temp seals)
  • steam valve: on machines than can froth milk (for cappuccino) it redirects steam to a separate pipe that goes into the milk cup
  • scale: hard water residues, usually calcium carbonate. It deposits and stops water flow
  • dispenser: sits above your coffee cup(s) and dispenses coffee into it
  • drip tray: sits underneath your coffee cup and catches spillage
  • sensors - they detect stuff: mechanical sensors or limit switches, magnetic sensors for checking covers, water sensors for sensing water, speed sensors (also magnetic) for checking motor rotation, flow sensor for measuring quantities of flowing water
  • covers: doors that can be opened for user-servicing the machine. It can mean the assy door (right on a Talea Giro), hopper cover (top), waste basket (also right, the lower portion), water reservoir (left)
  • priming: pipes should not have air inside them, so water/steam is pushed through them to get them ready.
  • water pump: steam alone is not powerful enough to push water through the unit, so an additional pump is used.
  • heating element/boiler: fills up with water, has a low-resistance wire that heats up the water. It also includes a temperature sensor and an over-temperature fuse. The fuse will disconnect if water goes above a certain temperature. The boiler does not work with air.

The function of the coffee machine: water and coffee beans go in, beans are ground, water is heated to a boiling point, pumped as a steam, the ground coffee is compressed, steam is passed through the ground coffee, through the dispenser and into the coffee cup.
The used (spent) coffee is then pressed, the resulting waste water goes the water waste bin, the (now dry) spent coffee goes into the coffee waste bin.

Water circuit: reservoir ->  boiler -> pump -> assy -> ground coffee -> coffee dispenser -> cup.

On cold startup the machine does several things:
  • The covers are checked to see if they are closed
  • The water reservoir is checked to see if it has enough water
  • The assy is rotated to one limit and back to the other limit. This resets it to a 'ready' state
  • The waste basket is checked to see if it's empty
  • The coffee counter is checked to see if it's above a limit
  • The water heater is turned on
After everything above is successful and the water reaches its boiling temperature, the unit does a 'priming' step:
  • The assy rotates to the 'brew' position
  • The water pump is turned on
  • Water goes through its normal circuit and the flow is measured
Cold startup means the machine has been turned off for at least 1h.
Warm startup - heating element/boiler is still warm - does not do the priming step. You should use cold startup for diagnosing.

Errors before the priming step

Easy steps

The covers are not closed - check all doors. Remove and replace the water reservoir. See if some beans are not blocking the doors or sensors. Use a strong magnet near the sensors to "fool" the unit into sensing that the doors are closed.
Check to see if the unit does not have any water inside it, especially under the waste bin.
Check to see that the water reservoir has enough water. The unit will want to make sure at least one (large) cup of coffee water content is there.
If this happens after a cleanup: check the assy, on my unit is has an arrow on the left (inner) side that has to be pulled up in order for the unit to close properly. Use the manual for this.

Harder steps

The water does not reach a boiling point. This is signalled by the yellow LED flashing continuously. It can mean that either the temperature sensor is broken or the heating element inside the boiler is broken.
The assy cannot reach its limit switches. It means that it's maybe blocked by something or it needs a bit of oil. Take it out and try to manually move stuff. I use the lever on the bottom of the assy on my unit. The assy motor might be broken - this you can detect if the assy is not trying to move at all. Or the limit switches are corroded/broken. You can sense this by listening to the motor trying to move too much after it's normal silent period.

Errors after the priming step

So the unit has turned on and passed its initial checks. It waited for a while, heated up the water and tried to do a priming step.

The unit remains silent

If there are no errors on the screen/LEDs then likely the heating element or sensor died out. Or you shut it down while it was still in an error state and it remembered that. Since it's a costly replacement, check the steps below, it cannot hurt.

Check to see if the steam valve is on the normal position. If it's even a tiny bit off the unit will detect the switch as erroneous and will not continue.

Did you hear any loud(usual) noise from the unit?

This probably means that the boiler is working, along with its temperature sensor, the pump is working.
The unit will check the flow meter now and it determined that not enough water goes through. 90% percent of the time this means that there is scale (carbon deposits) inside the pipes. Have you descaled the unit properly? I usually run 2-3 reservoirs to get it done properly. Using a filter does not exempt you for doing a descale, I learned that the hard way.

9% of the times it means the unit cannot pull water through: either the hard water filter (inside the reservoir) is too tightly packed with granules (aftermarket filter) or there is still air inside the system.

If there is air inside the system then you need to use the steam valve and the 'water drop' button to force water through. Try to do this in steps that last <10 seconds as to not overheat the pump.
If the filter is an aftermarket one (or DIY) try to remove it and do the step above without the filter.

The remaining 1% means there could be some issues with piping.

Errors during usage - coffee is not ground

There are no errors on the display, the unit has enough water and coffee beans. You try to make a coffee, there are some noises but nothing happens - you can hear the assy moving.

The grinder motor is not moving

Have you taken the unit apart? Check to see if you haven't pinched any wires and every connector is back to its place.
The cover might be off - check to see there aren't any particles blocking the sensors. If this is the case the assy motor would also not be moving.
If the machine goes through the [assy] motions as normal but it does not grind you can assume that the grinding motor is broken or the wires/fuses are broken.

Grinder motor is moving, coffee is not grinding/moving

It might mean there is a problem with your grinding wheel - too loose, something blocking the way or the the wheels/shaft connecting the motor to the grinding wheel might be broken.

Grinder motor moving, coffee getting ground, then wasted (without water being pumped)

Does the coffee makes its way to the assy? This is where you need to learn the sounds and see if the 'compression' step happens, this is when the assy moves ground coffee to the compressed position.

If there is no 'compression' step: the grinder speed sensor might be broken, there is no coffee, the setting for the grinder is too fine (grinder overload), grinding wheel is broken, grinding wheel is somehow slipping. Assy might be broken/misplaced, limit switches for assy might be broken.

If there is a compression step: does the water pump start? I assume so, see steps below. If not, then I don't know (yet), during the priming step the water pump should start.

Water/steam is being pumped, ground coffee gets dumped without getting into the cup

This might mean there is a flow restriction. Are you sure you've descaled the unit?
It can also be triggered by the ground coffee being too fine - water/steam cannot get through at an acceptable rate. Adjust the grinding ratio (coarse/fine) and see if it cures things. This can usually be adjusted through a knob inside the hopper, see the manual for this.
Coffee might be too 'fat', make sure you use coffee beans designed for automated coffee machines.

Some pipes might be disconnected or floating or they might've burst from pressure. Can't help you.

You can hear steam and water going in, no coffee coming out

The dispenser might be clogged, with scale or coffee deposits. You can buy a small wire brush that can clean it. It's a wire with bristles on it, like a bottle cleaner, around 5mm (0.2") in diameter and 25 cm (10") long. You run this wire through the dispenser (from below) until it reaches the inside of the unit and you can see its end (with the assy taken off).
If you are in an emergency situation perhaps you can find some plastic bristle wire, from a brush or something. Do not use a bare metal wire! Nylon wire would be a good choice.
This would happen especially if the unit has been sitting unused and unmaintained for a while.

You can use a compressed air can for checking flow and unrestricting it. It's gonna be messy.
The plugs/piping going to the dispenser might be broken.

The dispenser on my unit has an 'Aroma Selector' knob. If it's turned all the way to the right try turning it all the way to the left. With aroma selector turned all the way up the coffee flow is severly restricted.

If there is water coming out of the steam (frothing) pipe instead of the dispenser it means that the valve is broken. Replace the valve or plug the hole completely if you don't use it.

If there is water beneath the unit then: is the water black? Check the above steps. Is it clear? Check the complete water flow from the reservoir.

Check the assy, it has a [stainless steel] filter that keeps the ground coffee out and lets water through. It might be clogged, dirty or filled with deposits.

Coffee too weak

Check the aroma selector knob (in front of the unit, on the dispenser).
Clean the assy with tap water, check for coffee deposits.
Check if the water isn't following the correct path - use magnets to keep the door open and see what the unit does.

Coffee too small

See steps above, there might be a water restriction or a leak.

I press the coffee button, nothing happens (descaling)

The unit has a counter for descaling. After a certain number (200-500) the unit demands a descale. It's recommended you do this ahead of time anyway. If you're cheap you can use vinegar. If you're even cheaper, you can run the spent liquid through the unit a few times. Since it's hot, it helps even more with descaling. However, don't do this on the first cycle, use the 'second water' for this since it's a lot cleaner.

My descaling procedure - even though I use a filter anyway: every 4 months fill the tank with clean water (remove filter first!), add the recommended amount of descaling agent. If I run it sooner (every 2 months) I use household vinegar, about 10 teaspoons for 1L. I run the descale cycle once, dump the wastewater.
I then refill the tank with the same composition, run through the cycle, collect wastewater, use it in the tank (without filter!) for another 3-4 times.
Since my unit has been 'customized', the waste water is collected in the waste water bin instead of going through the steam pipe. But in your case it will likely go through that and you can collect it in a cup.
Procedure: I press the 'water drop' button on the unit that pumps water out instead of steam. I then rotate the steam selector knob to the 'frothing' position. You need to note that this does not clean the dispenser unit, you'd have to do that separately (with a small brush, see above).
I run this step for ~15 seconds and then rotate the steam knob to the normal position. I check the waste water: if it has black particles I throw it away, if it's clean I dump it back into the tank.
The 15 seconds are there to make sure that the wastewater tank does not overflow.
I run the steps above for a few times (3-4-5) and then empty the tank completely, refill with fresh water (no filter). Run the cycle once (15 seconds), replace the water filter, run through the whole tank. This ensures that your tank will not get soiled with descaling agents or vinegar.

There's (clear) water underneath my unit

Check the tank seals. After a certain age, the tank must be 'slammed' into place rather than gently pushed in. I've reinforced the ones on my unit by using some extra o-rings, 'fresh foil' and a pen spring.

There's (dirty) water underneath my unit

Again, this is mostly age-related. See if you can identify where the leaks come from. In my case, a piece that connects the dispenser to the assy is broken. It can be alleviated by turning the aroma selector down a notch.

For both of the above problems: you can either live with them, buy spare parts or get the unit serviced. It's not planned obsolescence but parts do eventually wear out.

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