Fluctuating Brew Pressure on 969.coffee Elba

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
mechanicflunkee
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#1: Post by mechanicflunkee »

Hi everyone,

Thank you in advance for any help, I am feeling lost after a routine cleaning.

I have been using a new (to me) Elba 3 for over a month without any issues but am now suffering from significant fluctuations on my brew pressure gauge. In the past, brew pressure would generally ramp up to 9 bars fairly smoothly when pulling a shot. When backflushing, it would briefly hold at 6 bars and then stay steady at 10 bars until I released the water.

Recently I was hearing fluctuations in my pump while pulling a shot - it would engage at a normal volume, weaken for a few seconds, then pick up again. Even though it didn't change these pressure readings too much, it bothered me enough that I decided to at least open up my group for a first cleaning to see whether I had reason to believe (wrongfully or not) that there may be scale from the previous owner that could have caused problems elsewhere. I graduated from a Gaggia Classic so scale as a potential indicator of issues is not unfamiliar to me.

However, the Elba's grouphead was generally clean and after performing some minor cleaning (light scale removal and relubrication), brew pressure changed entirely. My machine now struggles to reach even 8 bars for brewing or backflushing alike. When I tested with the blank disc, the pressure reading would hold at 3 bars for quite a while before slowly reaching 6 or 7 bars, 8 at a max if I chose to leave the lever up for a while.

Has anyone suffered from this before? Some initial thoughts and notes:
  • I initially believed I might have not tightened up different components of the group head enough upon reassembly. I noticed minor leaking at first so I retightened and saw the slightest improvement (possibly 1 bar of pressure increase), now I'm worried that I might even be overtightening in my attempt to rectify the issue.
  • The light amount of scale I took off might have gone elsewhere and caused issues? However, I thoroughly flushed as I went, soaked components in Cafiza, and even emptied and refilled the boiler to see if there was other scale inside but nothing of note came out.
  • A separate point of note is that I also started to briefly hear a slight hiss during machine warmup. I opened it up and saw that what appears to be a pressure relief valve on top of the boiler started to let off a little steam for a few seconds but wouldn't do so again when the machine was at temperature. I haven't noticed any decrease in pressure from the steam wand and the boiler pressure stays at its normal level of 1.5 bars.
I love this machine and have been enjoying it ever since it came into my possession, I would really appreciate any help from the community and I'm sure my partner will also be thankful to not see me stand around this machine scratching my head all day. It goes without saying but I'm more than happy to supplement with photos, videos, additional notes, etc. as needed. Thank you!

JRising
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#2: Post by JRising »

mechanicflunkee wrote:
  • The light amount of scale I took off might have gone elsewhere and caused issues? However, I thoroughly flushed as I went, soaked components in Cafiza, and even emptied and refilled the boiler to see if there was other scale inside but nothing of note came out.
  • A separate point of note is that I also started to briefly hear a slight hiss during machine warmup. I opened it up and saw that what appears to be a pressure relief valve on top of the boiler started to let off a little steam for a few seconds but wouldn't do so again when the machine was at temperature. I haven't noticed any decrease in pressure from the steam wand and the boiler pressure stays at its normal level of 1.5 bars.
I think you have nothing to worry about based on the above, but I may be confused.

Cafiza is a detergent, not an acid. It is for cleaning, which you seemed to want to do, but it really won't have any impact on scale build-up. It's not a decalcifier.
Secondly, a vacuum breaker releasing steam as the boiler approaches boiling point is normal, the water in contact with the element is boiling even before the majority of water in the boiler is, so some steam will be generated. So long as the vacuum breaker closes before the whole of the boiler water is boiling, and the valve doesn't leak when closed, your vacuum breaker is fine.

Back to brew pressure fluctuating: Does it seem like the normal fluctuation of a small machine with 16 or 18 gauge wiring and a vibe pump fluctuating in time with the element coming on and off? If it's similar to that, but extreme, then you probably have a switch (main power switch or brew switch) that is building up carbon on the contacts and becoming a significant voltage drop in the pump circuit.

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mechanicflunkee (original poster)
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#3: Post by mechanicflunkee (original poster) »

Thank you for getting back to me, I really appreciate your help.

To your point about Cafiza, thank you for the clarification. I was in a situation where I didn't have any decalcifier on hand (citric acid, Dezcal, vinegar, etc) and figured this would be better than nothing for general part cleaning but it does seem silly in retrospect. For actual scale I removed whatever was easily removable with a brush or cloth but can go back with proper cleaning solution shortly.

Also thank you for the note about the vacuum breaker - that could be a situation of never having noticed before so now I'll stop worrying about that aspect.

For the brew fluctuation, the fluctuation doesn't feel like it's correlated with the element switching on and off but I may be misinterpreting. I just took a video doing a test back flush so you can see and hear what I do. It feels like there's a noticeably lower flow rate from the group head relative to the last month when a similar back flush would rise to 10 bars in seconds. I'm curious for your thoughts about whether you still think this is tied to carbon on the switch contacts.


JRising
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#4: Post by JRising »

I don't see any indication of pressure fluctuating, but the video is awfully short. Pressure never gets a chance to plateau after filling the preinfusion chamber and reaching its max.

If you're talking about the tiny drop in pressure when the gauge gets to 3.25, then drops back to 3.1, then continues to rise... I would attribute that the the opening of the pre-infusion valve, that little bit of energy is consumed pushing the valve off of its seat, then it is held as the preinfusion chamber slowly fills and the pressure rises fairly linearly.
All looks good in that video, to me.

mechanicflunkee (original poster)
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#5: Post by mechanicflunkee (original poster) »

Your insight about the preinfusion chamber helps, mechanically speaking I'm working on it but you definitely know the inner workings better then I do so thank you again.

After my most recent pass tightening up the various parts of the group head it seems like the fluctuation issue isn't as pronounced as it was before. However, the brew pressure itself is still notably low compared to my earlier experiences. Maybe I'm just doing a poor job of articulating an issue with the sound of the pump and flow rate. I just took a new video pulling a shot - prior to the cleaning I used the same grind setting with a 20-30 second shot at a consistent 9 bar reading, now the situation is changed entirely. Greatly appreciate any thoughts you have as to why the pressure is comparatively low.



By the way I tried to act on your advice of cleaning the contacts for the switches. I was able to do so for three of the four contacts (two for the power switch, one for the brew switch). The last connection was so tight that I didn't feel I could confidently remove without potentially damaging the wire, that could be a sign that there is a carbon issue? The fact that symptoms of this potential issue could rise to the surface after a group head cleaning still has me a bit puzzled though, not sure if there's a video or thread you recommend I check out to understand better.

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cafeIKE
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#6: Post by cafeIKE »

Regarding the switch contacts, did you take it apart? Or just reseat the wire connectors?
If the former, you need a new switch. Contacts cannot be 'cleaned'.

JRising
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#7: Post by JRising »

A grouphead cleaning could make it easier for the preinfusion valve to un-seat, thus less noticeable drop in gauge pressure when it occurs...
CafeIke is correct about what I meant by the Switch Contacts. The moving parts inside the switch that open and close to "make or break" the circuit. Each time they "open", they spark and the burnt air in that little flash of light we see deposits a tiny amount of carbon on the contacts. In time that creates resistance, resistance in a circuit becomes it's own little heater (the element is just a well designed resistor in insulation and copper armor). Eventually electrical contacts in a switch get bad enough they'll burn themselves out. Wow did I ever go off on a tangent...

I actually started this to say that I don't think I hear anything weird with the pump in the video. And it certainly appears to be working beautifully. Is the coffee not good?

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mechanicflunkee (original poster)
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#8: Post by mechanicflunkee (original poster) »

CafeIke, thanks for jumping in to assist - I messed up the part terminology, I did not actually take apart the switch. I reseated the wire connector after checking to make sure that the metal tabs were free of any carbon or residue. It seems I did that for nought but at the very least now I'm more familiar with my machine, thank you both for the explanation about switch contacts.

I think based on everything I heard so far, the most likely culprit is that something was aggravated during reassembly of the group, whether that is the pre-infusion valve being unseated or wasting my time lubricating gaskets that were more worn than I was aware of and it's creating a loss in pressure somewhere. If the pump is in good shape and the electronic components don't appear to be giving me any trouble, my thought is to go through the process of replacing these gaskets. The machine is a few years old already and I'm under the impression that this is the first time it's being serviced so the idea that they are on their way out isn't so farfetched.

The coffee tastes great to me, it's just a matter of me obsessing over the big change in my pressure reading haha. If I'm drawing an incorrect conclusion please let me know, but otherwise I'll order the parts and update after I make the swaps. Thank you both again for lending your expertise and helping me think through this!

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cafeIKE
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#9: Post by cafeIKE »

Replace the gaskets and the valve brass as they wear down. FWIW, I do a full rebuild about every five years of making three to four espresso per day.

Be sure to get OEM or guaranteed 100% compatible parts as not all rebuild kits fit all machines.

mechanicflunkee (original poster)
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#10: Post by mechanicflunkee (original poster) »

Hi everyone, I have an update for the machine, unfortunately not with any significant improvements but maybe hopefully with a bit more process of elimination.

I ordered replacement brew, drain, and exhaust valves for the group head. When I looked at each old and new part side by side I realized the old gaskets were in worse condition than I originally assessed so thank you CafeIke, you were definitely right to recommend replacing. It was great to tick off from my maintenance list but I didn't notice an improvement to the flow rate and brew pressure issues.

I also soaked the mushroom valve and particle screen in a 50:50 water and vinegar solution for about 10 minutes to remove the limited remaining scale and any potential obstructions in the jet. It seems it helped others on this forum but aside from lightly better looking parts, I still haven't seen any improvement.

After these dead ends I decided to take a more accurate reading of the flow rate. Whole Latte Love indicated that it should take about 15-20 seconds to fill 4 oz. My reading was closer to 24 or 25 seconds. Brew pressure also still hovers at around 4 bars for the majority of the shots I pull which is consistent with past performance.

I know we mentioned the pump earlier and the feeling was that it sounds fine, does this new reading on the flow rate change that opinion at all? Thank you all for your help with this, I'm still feeling a bit lost but the solution feels close. Maybe there's another screen somewhere in the machine that could be gunked up?

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