La Marzocco GS3 - Steam Boiler Temp Probe Unconnect Msg

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
rajivsab
Supporter ♡

#1: Post by rajivsab »

Hi everyone. My GS3 is acting very strangely and I had to turn it off since I was afraid water had leaked into brain box. It is programmed to start @ 5:30 am and set to turn off at 10:00 am daily and it has not failed me once. Serial is 0245 from 2007. Thanks to all the experts I have upgraded / repaired many critical components but it has been two years since I touched the machine and I think time has caught up to me and I need to fix some things since the machine is on the bench tonight! I upgraded the OPV to drain into the drip pan in 2016. In 2019 I also cleaned out my steam boiler of crud and replaced the seals on both sides and I also replaced the check valves on the right hand side per this thread:
Steady leak from La Marzocco GS/3 tea dispenser

Now for the new series of problems: yesterday after 10:00 am when the machine turned itself off, displaying "OFF" it was making some hissing noises instead fo being silently cooling and I realized the machine was not really off since it was making these noises like water was moving and trying to heat. So I hit the power button in the back and turned it off. This morning when I turned it on the same noise like water heating moving appeared and the machine went into overdrive overheating and displaying the T.Probe.Uconnect/Steam.Boiler Temp error message. I think I heard something pop (check valve) after it had been on for an hour. Lots of steam in the drain pan but no water flow of any kind. Not that I noticed since I have added a drain but I do not believe there was any water leaking. The fill probe did trigger and it tried to fill the tank just for five seconds. The machine was able to brew coffee but the temp shot to 200 degrees and the tea dispenser water was cold but the steam was very strong.

I opened up both sides, there are no visible leaks other than on the steam boiler left hand side the infamously leaky ball vale has some hard deposits but that was already there when i last inspected the machine. Pictures of the boiler from both sides shows a clean no leak situation. The right hand side of the steam boiler also clean. The OPV tube was intact. Then I opened the brain box and there was no water intrusion IMO. I had taped my Brain box tight to ensure water would not get in. I am not ruling out contamination of the board. What I do know is when I toggle the back switch to ON, the machine reads OFF, but instead of silence you can hear the noises you hear when the machine warms up and it behaves like it is on and the displays reads "OFF" but water os flowing when it should not be. That seems like an electrical problem or a check valve is open 100%. I removed the ball valve, drained the boiler and noticed a tiny amount of crud but did notice some dark brown water at the bottom of the tank like coffee stained water - very dark and cloudy water in the steam boiler - scary. See pictures. So I am afraid I do not know what the problem is? Did water from the coffee boiler reverse into the steam boiler? Could it be the Solid State Relay in the brain box? Is it the temp probes faulty? Is the fill probe faulty? Is it the check valves? Which ones? In the earlier post I made in 2019, I had a lot of crud in my boiler. I use filtered water so there is no chance the particles get thru but the quality of the water may be causing extra crud in the boiler which may have caused this crash and blew one of the check valves? Maybe the problem started with he fill probe. I need my esteemed colleagues on thsi forum to help me:). Deeply appreciated.

Last observation: Single Shot button has gone missing and I do not know where to get a replacement. I was thinking of printing the image on glossy card stock then shrouding the square piece in Clear Silicone Sealant and gluing it in place but I doubt I can get it to match the other buttons. Any ideas here?

I do not know where to start diagnosing and given the machine is on the bench, it becomes more daunting to get this back in service. Thank you for your assistance and helping me.










Cerini Coffee & Gifts: official US importer for Olympia Express
Sponsored by Cerini Coffee & Gifts
User avatar
Peppersass
Supporter ❤

#2: Post by Peppersass »

There's appears to be evidence that water has been leaking from the ball valve into the brain box: white mineral deposits under the valve fitting, brown deposits on the cover of the brain box.

I saw something similar when my ball valve leaked. There are a couple of small holes in the chassis floor near the ball valve that allow water to drip onto the cover of the brain box. From there it can make its way down the screw holes or over to the cable opening.

You can't tell if the logic board is contaminated just by looking at the top. You have to remove the board and check underneath. Photograph and mark the wires so you know where to reconnect them.

It's likely that contamination on the logic board has caused the temperature probe unconnected message. It's possible that the probe has gone bad or its wires have been compromised, but that's less likely than logic board contamination, given the evidence of leakage.

I've never seen the symptom where the machine says it's off but water is flowing and heating. But contaminated logic boards can do weird things. It's also odd that the machine is complaining that the steam boiler temperature probe is not connected, but continues to heat the water. I would think the firmware would shut of the heating in that case. Again, contamination may be causing the machine to misbehave.

The pop you heard after the machine was on for an hour was likely the OPV triggering. That would explain vast amounts of steam pouring into the drain box. The OPV will trigger if the steam boiler temperature exceeds 3 BAR. This can happen if the steam boiler overheats or if it overfills due to a check valve failure or logic board contamination.

[Let's get some terminology straight: You mention that you upgraded the OPV to drain into the drip pan. That sound like you upgraded the vacuum breaker valve on the upper right side of the steam boiler to drain into the drain box, which is a standard upgrade that owners of old GS/3s should do. The vacuum breaker operates every time the machine cools down and warms up. The OPV is a safety valve that's in a metal can between the steam boiler and the coffee boiler.]

The presence of crud and dark/cloudy in your steam boiler is cause for concern (you mention a photo of that, but I don't see one.) I hope it's not as bad as the contamination shown in photos from your earlier thread. When you say you use filtered water, what exactly do you mean. What is your water source? Do you have one or more filters between the water source and your machine? What type and size filters? (microns?) If you have a carbon filter, did you flush it before use? Do you use a softener. The amount of white mineral deposit around the ball valve suggests that your water may be too hard.

It's possible you have multiple problems, such as logic board contamination, stuck check valves, stuck solenoid valves, etc. My advice is to start with the logic board. Once you get that straightened out, you should inspect the check valves to make sure debris hasn't contaminated them.

rajivsab (original poster)
Supporter ♡

#3: Post by rajivsab (original poster) »

@Peppersass Thank you for your thoughtful reply. Yes, I made a mistake on the OPV terminology. Indeed I did not change the OPV. I actually upgraded the vacuum breaker valve on the upper right side of the steam boiler to drain into the drain box. This system upgrade works despite a crinkle in my cable because the vacuum breaker brass outlet pipe is literally at 90 degrees to the side wall causing me to leave the side wall open by 2 cms so as not to crink the cable. In this iteration I am going to cut that brass outlet with a dremel so i can shut the side door 100%. I currently have two copper washers in there. Frustrating how the part does not fit.

DEPOSITS: As for the crud/cloudy water in steam boiler, I do not have a photo but I was referring to tiny scale pieces I found in the ball valve and quality of water extracted. I think my water is hard indeed and causing these problems. It is a bad situation since I only have a water filter only and no softener. I have to test the water and solve for this indeed.

FILTER:I have an under-the-sink mounted Everpure H-300 Water Filter Cartridge that feeds the sink-top water dispenser and the coffee machine inlet. I believe it reduces particles as small as 0.5 micron in sizeThe water source feeding the filter it is the house water line. XX is the only filter between the water source and the GS3. No softener.

LOGIC BOARD: I taped the screw holes and can tell there was no water intrusion from there. This is hard to debate and there is a high possibility this is the cause. I will remove the logic board carefully and mark the wires and take photos and report back. How does one test the integrity of the logic board? I am still befuddled with the state of the machine in OFF mode. What if the logic board is deemed not contaminated and the OFF mode behavior continues? Isn;t that an electrical fault?

CHECK VALVES: When I upgraded the check valves near the tea dispenser I think I re-used old ones so that could be a failure point. Now that the machine is on the bench i am willing and able to take it all apart if needed. Is there a diagram that shows all the check valves in the system? I think they all are located at the right hand side. I have two brand new older versions and will likely need to order some more. Is it OK to use the old and new models on the same machine?

Thank you to this group and all its dedicated members.

JRising

#4: Post by JRising »

Maybe the 220V machines don't have it because their Powerboard relays aren't expeted to burn up so quickly running at half the North American amperage. In North America the SSR sits on the same bracket that holds the Powerboard.


Sorry for being mis-leading.

User avatar
Peppersass
Supporter ❤

#5: Post by Peppersass »

Without a schematic, deep knowledge of the circuit design and test equipment, there really isn't an easy way to test the integrity of the logic board, other than replacing it with a known good logic board or testing yours in another GS/3.

Rather than repeat my advice and instructions on determining whether the logic board is contaminated, and dealing with it if so, I've created a new photo-illustrated thread called La Marzocco GS/3 Logic Board Water Contamination. Hopefully that will answer your questions and provide some guidance on what to do. If not, feel free to ask.

rajivsab (original poster)
Supporter ♡

#6: Post by rajivsab (original poster) »

Thank you @Peppersass. I reviewed the post on inspecting and protecting the Logic Board. Very insightful and well written. I have not made any progress. Fortunately for me the machine went out on the day i decided to do a cleansing and be coffee-free for a special ceremony this weekend. It has been a journey and withdrawing from coffee is hard. Headaches on day 3 and 4!! I am looking forward to first removing the board and inspecting the bottom and top of the boards and box with a magnifying glass and then drilling holes and protecting the board for the future. Agree with you: this ball valve design is so finicky and they could not have thought of a worse design choice by placing the brains of the machine under the guts of the machine. Three questions:
1. Can you comment on the diagram of where all the check valves are located in the machine? How many should I replace/order?
2. To clean the boiler wall:
- Shall I remove the seal on the left side then remove the heating element, fill the boiler with a decalcifying solution and clean out the gunk with a brush?
- Or keep the seal intact and use the cleaned up ball valve to fill and drain the boiler with a solution?
- Which solution shall I use? I have the PURO CAFF ESPRESSO MACHINE CLEANER Powder? What should the ratio of powder to water be and duration of time I leave the boiler to soak in?

I will post pictures shortly.

rajivsab (original poster)
Supporter ♡

#7: Post by rajivsab (original poster) »

@peppersass, I removed the logic board according to these instructions: La Marzocco GS/3 logic board water contaminationand here are the findings:
1. It looks like I have a poor mains connection (white wire) that was close to melting, likely a loose connection. Worse than the connection shown in this post by Jake_G Changing the battery in a La Marzocco GS3 logic board. I need to repair the cable connector and ensure a tight fit upon reassembly. It seems the wires are about to drop off that end pf the cable and a weak connection. The pin on the power switch was also bent at the white wire. See pictures.
2. There is no evidence of water intrusion on the bottom of the box under the logic board. no visible stains of any kind.
3. There seems to be one large sticky blob of left over flux/water deposit on the under side of the board directly behind the three battery soldering terminals. It looks like either the solder has corroded or the installer of the new clock did a poor job and left a mess behind or this blob is a failure point. Maybe the battery is slowly leaking sticky stuff and on its way to frying. Is there a way to tell if this is the original battery?
4. The solder on one big pathway seems to be fading/evaporating/chipped and likely not a failure point.
5. The lower shorter length ribbon cable in the back towards the bottom seemed loose when I was opening the logic board.

I will obtain 99% Isopropyl Alcohol and clean the blob with a Q-Tip to see if I can remove it. If it comes off and the burnt spots fade, I may be OK. My clock is not acting weirdly but I do recall programming the main message / greeting on the machine and the programming would not accept all the names I wanted to give it. i would enter x and it would display y. That could also be a loose connection. I do not think I had water intrusion based on the bottom of the board not having any patches or stains. The top of the board is pristine and looks brand new.

Hopefully this step gets me one step closer to diagnosis. Looking forward to your observations.












BPlus: turning your coffee spirit
Sponsored by BPlus
Bmccall
Supporter ♡

#8: Post by Bmccall »

Check with voltage coffee supply. They can order you the missing single shot button.

User avatar
Peppersass
Supporter ❤

#9: Post by Peppersass »

rajivsab wrote: 1. It looks like I have a poor mains connection (white wire) that was close to melting, likely a loose connection.
I had this problem with one of the other leads to the power switch. As AssafL said in his comment on Jake's thread about changing the battery, heat from the switch reduces the springiness of the connector, causing an incomplete connection, and the resistance causes more heat, more reduction in springiness, etc. In my case, the heat buildup would intermittently trip the thermal breaker in the power switch.

Crimp a new connector on that wire and you should be fine. I don't think the bent pin on the power switch is a problem unless the plastic is cracked and it looks like the connection inside the switch could be compromised.

It's conceivable that the AC voltage dropped enough to affect the logic board DC voltage regulators, which in turn produces the symptoms you're seeing, but that's more likely to cause a reboot (Jake has a thread on that one.)
rajivsab wrote:2. There is no evidence of water intrusion on the bottom of the box under the logic board. no visible stains of any kind.
What are the white spots all over the bottom and sides of the brain box? I ask because the spots are the same color as the mineral deposits under your leaking ball valve. Are they deposits you can scrape off or are they just places where the black has worn off the plastic? The former would indicate some sort of contamination.
rajivsab wrote:3. There seems to be one large sticky blob of left over flux/water deposit on the under side of the board directly behind the three battery soldering terminals.
I think this might be adhesive left over from the "gumdrop" shown in the photo in Jake's battery replacement thread. The gumdrop in his photo is on the closely-spaced traces near the battery solder point, not over the solder points where the stain is on your board. But it looks like the right size and there's no evidence of the gumdrop having been placed where Jake's is. In any event, I suspect the residue is harmless. I don't see any evidence on top of the board that the battery has leaked.

I'm not sure, but I think the purpose of the gumdrop is to prevent the board from flexing too much, and possibly breaking a trace, when connectors are pushed on.

It's a long-shot, but since the gumdrop is missing, I would carefully inspect all of the traces and solder joints on the board for any evidence of cracking due to stress on the board. Such cracks can be very small and hard to find. Typically, they cause intermittent behavior as continuity is lost or partially lost from vibration or temperature fluctuation. Usually it's easy to fix a crack by scraping away the coating and bridging the crack with a wire soldered to both sides of the trace, or just using a blob of solder to bridge the crack.
rajivsab wrote:It looks like either the solder has corroded or the installer of the new clock did a poor job and left a mess behind or this blob is a failure point.
Are you talking about the solder joints for the battery? And when you say "installer of the new clock" do you mean installer of the new battery? If you really mean installer of the new clock, that would be the real-time clock (RTC) chip, which has been known to fail after water incursion. Which do you mean? Are you not the original owner of the machine? Do you know of any work that was done on the logic board?

In any case, I doubt those solder joints are the problem. As far as I know, the battery only keeps the RTC powered when the machine is off so it'll remember the time, and if the battery connection is bad you would only see issues with the time not being correct.
rajivsab wrote:Maybe the battery is slowly leaking sticky stuff and on its way to frying. Is there a way to tell if this is the original battery?
I don't think the battery is leaking. The solder joints look a bit rough, so maybe it's not the original battery.
rajivsab wrote:4. The solder on one big pathway seems to be fading/evaporating/chipped and likely not a failure point..
I don't think this is a problem.
rajivsab wrote:5. The lower shorter length ribbon cable in the back towards the bottom seemed loose when I was opening the logic board..
This might explain the problems you had with data entry, but I think you would have seen other symptoms in the display or with the buttons. Make sure the connector is firmly seated when you close the brain box and reinstall it.
rajivsab wrote:I will obtain 99% Isopropyl Alcohol and clean the blob with a Q-Tip to see if I can remove it.
I don't see any harm in doing that. You might as well wipe down the entire board to make sure there are no mineral dried mineral deposits that you missed or are too small to see.

Why did you circle the area to the right of the battery mounting points? Are those components showing signs of burning or is that just flux that boiled up onto the component from the solder?

rajivsab (original poster)
Supporter ♡

#10: Post by rajivsab (original poster) »

Thanks @peppersass. Answers below. What type of connector shall I put in place of the burnt one? I have no idea what to buy/install?

The white spots all over the bottom are overhead light reflection. The sides of the brain box contain granules hardened very similar to the leak from the ball valve. I believe yes some water or hardened powder made it's way to the bottom but there does not seem to be any water stains on the surface.

I was talking about the solder joints for the battery that I suspected the previous owner installed but it looks like this was not the case. I am not sure where that gum ball went BTW. I have had the machine since 2014. I believe the previous owner I inherited this machine from (came with the house) was the first owner.

Yes I circled the area to the right of the battery mounting points because I thought those components show signs of burning but I think it is just flux that boiled up onto the component from the solder. I will check for cracks.

99.9% Isopropyl Alcohol is arriving today. I will coat every mm with it. Blow it with a cool fan. Inspect the board for cracks. Take pictures. Reassemble. Flush the steam boiler after cleaning it with descaling solution. Then I plan to inspect the check valves to and from the tea dispenser and replace with brand new ones (N=2) then I will reinstall the current ball valve.I do not believe I need to replace it. Should I? I also removed the fill probe and cleaned it - it had some scale deposits crumbles like salt. Then I will fire it up to see what happens and hoping the temperature probe U.Connect message does not reappear.

Anything else I am missing?