ACS Minima pump always on

Jack123

Hi everyone,

I’m having the following problem with my 2022 ACS Minima. After pulling the first shot of the day and preparing for another, suddenly the pump went on by itself (the brew switch was off and the 3-point switch was in the “both boilers” position), followed by the smell of a burnt plastic. No water was dripping from the group while the pump was running, and the shot timer wasn’t shown on the display.

I took the covers off and noticed two things: brew boiler leaks and scorch marks on both red ferrules of the Gicar’s pump connector. Please note that I wiped the burn marks clean prior to taking the picture (just forgot to take a photo of them right away).

I’m guessing what happened is that the leak went under the boiler insulation and managed to short the cables on the connector. I didn’t see any leaks below the boiler.

I left the machine unplugged for a week or so, to let it dry properly. Plugged in today, the pump starts running when I hit the 3-position on/off switch, but no water is drawn from the tank. The pump sounds “dry” (the pitch is different when it’s filled with water). The display goes through the usual power-on sequence (displaying the firmware version number and then the temperature of the boilers). I didn’t leave it on long enough to see if the boilers start heating. Oh, and also the burnt electronics/plastic smell is back, hard to say exactly which part it is coming from as everything is crammed together but I’d assume from the bigger Gicar box.

I am currently about 1kkm from the closest repair shop (no kidding) so would like to try fixing this myself. My homestead workshop is pretty well equipped, what I’m lacking is knowledge of diagnosing and troubleshooting espresso machines. It seems ACS Minima technical documentation is scarce, so I’m hoping to find some guidance from the technicians and experienced users on the forum. I’d appreciate any suggestions / instructions on how to diagnose which parts went awry, so I can order replacements from ACS of elsewhere.

Thanks in advance!

DavecUK

Jack123 Need information

construction year of machine
location of black autofill cable from Gicar Box, frame or boiler (one wire is to autofill probe, other to boiler
Inspect above cable, is it’s termination rusted from boiler water leakage
type of water used
is cable on autofill probe loose (as you don’t show a photo of the service boiler
did it suddenly start happening or has service boiler over filled before, or pump AL message come on (due to auto shutoff after 2 minutes
when was it last serviced/inspected before this
Are the pump connectors loose, as pump only takes 50W, so can only burn if loose (arcing) or shorted
turn the machine to brew only, does pump start running, turn on the actual brew switch, does water come out of the group
check the autofill solenoid wires, are they loose, connected, burnt, water damaged?

Jack123

DavecUK Hi Dave, I appreciate your reply. This is the information I have gathered so far:

construction year of machine
- 07/2022. I bought it new in February 2023, so it’s been used for less than a year and a half. Max 4 double shots daily, the machine typically stays switched on for about 2-3 hours, then off for the rest of the day.
location of black autofill cable from Gicar Box, frame or boiler (one wire is to autofill probe, other to boiler
- Dedicated connector on the frame. Difficult to take a picture as it’s located below the service boiler
Inspect above cable, is it’s termination rusted from boiler water leakage
- Visual inspection didn’t reveal any deterioration
type of water used
- Exclusively RO (typical 5-stage system which includes a mineralizing cartridge
is cable on autofill probe loose (as you don’t show a photo of the service boiler
- I tried to yank it gently and it stayed put so I believe it’s not loose. I was able to swivel the rod (probe) in its PTFE sleeve but it looks like it should behave this way?
did it suddenly start happening or has service boiler over filled before, or pump AL message come on (due to auto shutoff after 2 minutes
- It happened suddenly, no prior issues or error messages whatsoever
when was it last serviced/inspected before this
- Never
Are the pump connectors loose, as pump only takes 50W, so can only burn if loose (arcing) or shorted
- I tried pulling the cables, the connectors appear to be sitting firmly
turn the machine to brew only, does pump start running, turn on the actual brew switch, does water come out of the group
- The pump starts running immediately when the main switch is turned on. Water does come out when the brew switch is turned on. I made a quick video, also please note the leak appearing almost instantly.
check the autofill solenoid wires, are they loose, connected, burnt, water damaged?
- I’m not sure which one is the autofill solenoid, assuming the one located behind the service boiler. If so, the cables were not damaged by water. The connectors sit firmly.

DavecUK

Looks like you have 2 jobs

Leave the autofill probe wire as is…it should (moving within the teflon sleeve is normal, if it doesn’t, then the sleeve squish nut is too tight). The earthing wire (for the other half of the probe connection) from the Gicar should be earthed on the frame not the boiler.
Undo the copper pipe compression fitting connection to the brew boiler, then using a very well fitting spanner, use the flats on the elbow to remove that elbow from the boiler. Rappy rappy with a small metal object on the end of the spanner to shock break the threadlocker, which back in 2023 was probably permanent thread locker and hard to break free. Don’t damage the elbow, it’s nickel plated brass..not stainless. Then clean threads and refit using PTFE Tape, 7-20 wraps ish? Remembering it doesn’t have to be filly tightened down with PTFE, just tightish all the way in. This allows you to line up nicely with the copper pipe again.

Jack123

DavecUK I was able to undo the elbow and the temp probe (because it was getting in the way). I noticed both were covered in black grease. Wiped it clean, but then started to wonder: according to your knowledge, should temperature sensor be greased? If so, what grease should be used - Molykote 111, other? I’d appreciate your advice.

MediumRoastSteam

Jack123 - never heard of a temp probe being greased - there’s no rubbing or friction against anything.

Jack123

Thanks DavecUK and MediumRoastSteam

I’ve managed to seal all the leaks up, but both issues persist:

The pump starts running immediately after the machine gets turned on. I’ve run 10 power cycles (1 minute on, 2 minutes off) in case there was some water missing in the boiler, but to no avail - the pump keeps running.
The smell of burnt plastic / electronics - I can’t pinpoint the culprit though. There’s no smoke and I can’t seem to find any particular component whose temperature would stand out.

I made another short video showcasing the pump behavior:

I’d appreciate any further suggestions. What would be the next step you take to figure it out?

DavecUK

No…the black is normal for soft water…the extension you see on the elbow, prevents air in the brew circuit stopping the thermosyphon. Important if you ever need to buy a new elbow!!

MediumRoastSteam

Jack123 when you turn the machine on, and the pump runs, there must be water going somewhere. Where? Can you see if it’s ending up back in the tank or overflowing somewhere?

How do you know the fill sensor is working? If you disconnect it, what happens? Does the pump still run?

DavecUK

Check the return pipe to the tank coming from the expansion valve, lift this tube out of the tank and observe, is water coming out. It should be as, when the switch isn’t lifted to make a shot, the pressure is going direct to the sealed brew circuit and the expansion valve will open so this is maintained at 9 bar.

Just to elaborate on this

MediumRoastSteam How do you know the fill sensor is working? If you disconnect it, what happens? Does the pump still run?

If you disconnect the fill sensor, the pump will definitely run.,,,A quick test can be to disconnect the fill sensor wire and touch it to the boiler or the frame of the machine. A more thorough check is to disconnect the thin black Gicar earthing wire (which should be to the frame not the boiler) and the fill probe wire, then connecting them together…should stop the pump.

If it doesn’t, then I can only suspect the Gicar box itself is faulty (or there is a break in the wires, which you can check with a resistance meter) and unfortunately, it’s not such a cheap item! You actually do need that exact box from ACS as it contains custom programming specific to that machine.

One key point to make is that if the level in the service boiler is low and the autofill solenoid has failed (or bad connection)…the service boiler will never fill and the machine will constantly call for water…the test above will confirm this if connecting the wires immediately stops the pump.

Jack123

DavecUK MediumRoastSteam I appreciate your answers and suggestions.

Replying to your questions:

When I check the return pipe, the water is indeed coming out:
I disconnected both black wires coming out of the Gicar (one from the fill probe on the service boiler and the other from the earth which is located on the frame below and between the boilers - it’s a kind of a pin bolted on to the bottom plate of the frame; there is also a yellow/green thick cable from the main power connector attached to this pin, I mean apart from the thin black cable from the Gicar box) and then connected them together:

I hope these are the right ones @DavecUK. Anyway, the pump didn’t stop.

I also opened the Gicar box, hoping to find clues on the boards (there are two PCB inside, connected with a wide tape). There were no visible scorch marks or signs of overheating elements, but the smell of burnt electronics was prominent. Additionally, I’ve tested as many wires as I could for continuity (especially the two black ones coming out of the Gicar) but did not find any breaks.

If these tests confirm a faulty Gicar controller - do you by any chance know where can I get a new one? ACS doesn’t seem to have any online store.

DavecUK

Jack123 I also opened the Gicar box, hoping to find clues on the boards (there are two PCB inside, connected with a wide tape). There were no visible scorch marks or signs of overheating elements, but the smell of burnt electronics was prominent. Additionally, I’ve tested as many wires as I could for continuity (especially the two black ones coming out of the Gicar) but did not find any breaks.

If these tests confirm a faulty Gicar controller - do you by any chance know where can I get a new one? ACS doesn’t seem to have any online store.

Probably, but as it’s not cheap there is one last test if you have the equipment. It’s possible the wires or connector has failed. So with a resistance meter do a check for continuity. Pull the connector and check it’s little connections go open and closed circuit if you connect/disconnect the fill sensor and frame wire,

I can’t remember for sure, but I think there’s probe test points on the connector…..you will figure it out though. If that test proves the wire and connector are OK, it’s unfortunately Gicar box time, just contact Maria at sales@mevsrl.net.