La Marzocco GS3 - Steam Boiler Temp Probe Unconnect Msg - Page 3

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
rajivsab (original poster)
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#21: Post by rajivsab (original poster) »

Hello and thanks for the recommendation for the Chris Coffee system. I think that should get me over this hump. We are not going to install a whole house softener - it's not environmentally friendly with the large volume of water purging daily!

I checked the City of Santa Cruz website and the Chloride levels are way lower than I had guessed, updated water readings are:

Hardness: 12 gpg (Hach)
Iron: 0
Free Chlorine: 0.4
Total Chlorine: 0.15
pH: 7.5
Total Alkalinity: 240
Chloride: 26

Here are Endoscope images of the scaling on the heater elements and the tank. Looks like the bottom half of the tank is heavily scaled compared to the top half. It's pretty flaky on the heater element. Will the new cation system loosen the flakes? I think I should remove the right hand side heater element, which is on a higher axis and has more scale specially since I soaked the tank in scaling solution for 48 hours with the tank about 2/3rds full, descaled the lower heating element a little more.

Thanks for taking the time to review these new data points.

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rajivsab (original poster)
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#22: Post by rajivsab (original poster) »

The Easter Bunny brought me a surprise! While waiting for parts, and when I went in to clean the heating element and descale the steam boiler from the left hand side, I discovered the heating element was fried and compromised! Looks like a scene of out Jaws! The acidic water has eaten into the heating element. This could have gone south if I kept using the machine. Looks like this may be the cause of the T.Probe.Uconnect/Steam.Boiler Temp error message. And this could explain how the machine says it's off but water is flowing and heating. This would also explain the vast amounts of steam pouring into the drain box. And this explains the almost 2 tablespoons of crud in my steam boiler. The guts of the heating element are spewing crud into the water! Now sure how this is all related but I obviously need to replace this part. Could I have shorted an electrical component outside of the logic board? Anyone else with a 2007 machine who has experienced this amount of corrosion? Can't wait to get this thing started again with a new heating element and soft water with the cation filter! Thanks everyone.

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#23: Post by Peppersass »

No question that the heating element is toast and must be replaced. I've not seen such extensive scale damage to a GS/3 heating element.

In your prior post, you mentioned the "heating element" on the right side. That's not a heating element. That's the brew water heat exchanger (HX). It's a hollow copper tube bent into loops similar to the heating element on the right side. The idea is to pre-heat the cold water before it enters the brew boiler to improve temperature stability.

The damage to the heating element gives me concern that the HX tube could be damaged or on the verge of being damaged. It doesn't look too bad in the photos, though. Also, if there's a leak in the HX, the steam boiler will overfill, trigger the OPV, etc., and you've not reported symptoms suggesting that has happened (you initially reported a one-time pop that was probably the OPV triggering, but if the HX is leaking it would happen repeatedly.) Still, I would remove the HX for inspection and cleaning.

IMPORTANT NOTE: Removing the HX is trickier than removing the heating element. You must be very careful when removing and reinstalling the small tubes that connect it to the mixing block, and must be even more careful when removing and reinstalling the HX from the boiler. It won't come straight out, so you have to sort of twist it around to finesse it out of the hole. Don't force it. I say this because a member of HB broke his HX when removing from the boiler and had to replace it.

The split heating element might explain some of the symptoms you've reported, but not all of them. Rather, I think there's mounting evidence that scale or corrosion has severely compromised your machine. The evidence is strong that it caused the ball valve to leak, and now you know it has damaged the steam boiler heating element. But how can a broken heating element cause a Probe Unconnect message? The logic board is seeing an open circuit, and there are a number of possible causes: contamination of the logic board or corrosion of the portion of the temperature probe in the boiler. I'd remove the probe and inspect it for any obvious signs of damage. There could be a loose or disconnected wire running between the probe and logic board, but that seems less likely.

Further, I don't see how a broken steam boiler heating element could cause the machine to display OFF when it's actually on and heating the water. By the way, after re-reading your first post I'm not clear on what you mean when you say the machine is "moving water" when it's supposedly OFF. Do you mean the motor is coming on or is the water moving through the machine due to a valve being open and line pressure moving the water?

I ask that because one of the other strange symptoms you reported was cold tea water when there's plenty of steam. The only way I can see that happening is if there's a blockage in the tea water mixing block that's preventing the hot tea water from mixing with the cold water. Sure, if the heating element isn't working you would see the same thing, but you wouldn't have any steam.

I may be going overboard here, but if my machine had the symptoms of your machine, I'd probably disassemble it completely, thoroughly inspect every tube, fitting and part for scale or corrosion, get rid of every trace of scale, and replace all parts showing signs of damage. That's a huge job, but it sounds like you've done quite a bit of work on the machine previously, and you have the skills and tools to do the job.

Maybe someone else will chime in with different advice.

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#24: Post by Jake_G »

I agree with Dick.

With respect to the steam boiler temp probe unconnect error code, I will quote my earlier suggestion:
Jake_G wrote:Another step in troubleshooting the steam temp probe unconnected error is to swap the steam boiler and coffee boiler temperature probe cables at the logic board, assuming the error remains after IPA treatment.

If the error stays on the steam boiler, it is 100% a logic board issue since the steam boiler input will have coffee boiler probe and wiring connected to it and vice versa for the coffee boiler input.

If the error switches from steam boiler to coffee boiler, you have a legitimate issue with either the cable (relatively cheap to replace) or the PT1000 probe (not relatively cheap to replace) on the steam boiler. Swapping the cables on the sensors thenselves will then further isolate the issue. If the error switches back to the steam boiler, you have a bad probe. If it stays on the coffee boiler, yuu have a bad cable. Either way, you'll know where the problem lies.
The split heating element is certainly the cause of the muck in the boiler and could have caused minor issues with heating, assuming it wasn't shorted out, but it would not be a likely suspect for the temperature probe issues, nor the continuous heating of the boiler.

You can power up the logic board with the temperature probes connected, but the SSRs disconnected and continue to troubleshoot whilst the machine is torn down. You'll just want to connect the wire for the level probe to a good solid ground to make the auto fill happy.

As for full tear down, that's a personal call. I did it, but then again I am also known for removing and disassembling the engine in a new-to-me used car when I bring it home. So, yeah. I've got issues. :lol:


- Jake

rajivsab (original poster)
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#25: Post by rajivsab (original poster) »

Thank you. I will try both your suggestions, Dick and Jake: inspect the HX, inspect for blockage in tea mixing block, switch the probe wires in the brain box. When I went to order a replacement heating element today, LM informed me there is a new 900W element that replaces the old 1,000 - 1,200 watt models sold by Voltage and Espresso Parts. Looks like the 900W models will be the defacto part moving forward until the old supply dwindles. I ordered the lower wattage model because this is what LM recommends. Is this one of those things I should ignore and buy the older model which is $30 bucks cheaper ($173 vs. $143) since I am a firm believer in "old is gold": they don't make stuff as durable as they did in the old days!

2nd question re: removing the scale in the tank I was thinking of dropping in 3.5 liters of a cleaning solution to clean the tank before removing the HX and the downstream pipes of the Hydraulic System: I plan on using Citric Acid Powder, 60 grams in 3.5 liters and soak for 90 minutes twice then flush 4 times. It is the only way I see cleaning every inch of the steam boiler. I have the machine positioned sideways with the HX on the bottom side and I installed a new Ball Valve in place of the pipes leading to the tea mixer valve and using that as the bottom as my drain and using the heater element opening as the source for the bath at the top. Will any solution leak into the system downstream or will the check valves ensure the bath is limited to the steam boiler? Is my solution too strong? Assuming Stainless Steel and Citric acid are not harmful to each other.

Many thanks for assisting me on this journey.

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#26: Post by Peppersass »

I have never descaled my GS/3, so I have no expertise in the matter.

That said, I worry about two things with descaling an assembled machine:

1) Not getting every trace of acid out of the machine. If you don't, it may corrode the parts and result in even bigger headaches. If I was forced to descale a machine, I'd flush it many, many, many times, and even then I'd obsess over whether I had gotten all the acid out. (I have issues, too :D ).

2) Descaling can dislodge particles of scale that can get stuck in narrow openings, and they may not dissolve before you flush the machine. That'll cause more headaches. In your case, it's possible that metal fragments are suspended in the scale, and they could get lodged in narrow openings, will never dissolve and may be much more difficult to remove than scale particles. Again, more headaches.

These are the reasons I use a cation softener, which eliminates all hardness --- so I never have to descale.

When you have the machine in pieces, you can descale each part (tubes, valves, boilers, etc.) separately, making sure they're thoroughly flushed, acid free, and feee of any debris or contaminants.