Cimbali M21 Plus Overpressure Problem

[Zakal1]

Okay, just before I open it up, here is a photo I took of it the other day (before I did the cleaning for the ECB).

Can you tell whether that is a 24v model?

Also, looking at it now, it looks like the switch hasn't moved fully to the left, so maybe that was the problem after all.

[Javaphile]

If you want to get an idea of how close to failure the contactor is open it up and take a look at the contact points. From the behavior you describe it sounds like a points issue rather than a coil problem with it likely being only a single set of points maintaining contact. If all (3?) of the sets were maintaining contact the safety overpressure valve wouldn't be spitting out just a small amount of steam, steam would be blasting out of it. Each set of contact points supplies power to one heating element. I've not seen your exact model but typically there are 3 heating elements in the 2 group Cimbalis.

New the points are smooth and shiny. As they age they darken and become pitted and if left in long enough as shown in the posts I originally linked to will be eaten away by the arcing that happens as they connect/break apart. Depending on how bad the surface of them are you might be able to clean them up with a scotchbright type pad using as 'fine' a one as possible. In a worst case last ditch scenario to get it work 'right now' some sandpaper or a file. Also check the lubrication to make sure everything is moving smoothly.

The reality is if you have to work on the points it's time to replace the contactor as the problem will return, sooner rather than later.


Java "If ya wanna know ya gotta take it apart" phile

[Zakal1]

Okay, so remember i mentioned the poltergeists? well, they're back.

So I fired it up after giving it a clean with contact cleaner (and an hour long bake in the oven at 40C). No dice, had the exact same problem.

Turned it off as soon as I heard steam coming from the OPV, and opened one of the steamwands to full, and let it cool down. I wasn't able to do what noidle suggeested above as I had to leave for a bit so it basically cooled all the way back down again.

When i got back, i fired it up again to do the test. Got ready as the pressure built....then...."CLICK!". Element turned off. I checked the pressure stat, and it had just clicked off. The slightest bit of pressure "downward" clicked it back on, and "upward" clicked it back off. So it was sitting right on the sweet spot the pressurestat is obviously set to.


I stood there dumbfounded for a while listening to the loud click (which i now understand is most likley the tab in that contactor shown above switching back and forth) as the element was turned on and off by the pressurestat.

I would think it was the contact clean (and thus an ECB issue) except that it didn't work directly after doing that. It randomly worked again after failing previously, and i did nothing between the last fail and the most recent success.

Its been on for several hours now, clicking on and off by itself again.

Does this suggest that maybe the Contactor is on its way out, but isn't completely broken yet?


Also, I don't know if the gauge is accurate (because I think there has been something wrong with it for a while), but it now seems to be clicking on and off just under the 0.8 bar mark (according to the suspect boiler gauge). It feels like I have less steam than usual, but is there any other way to check boiler pressure without the gauge (i have ordered another one, but it will likely be a few weeks until it arrives).

I dont know why it would suddenly be shutting off at a different pressure than before. I took the pressurestat out to clean it, but i never adjusted the screw, so it should be the exact same setting as before shouldnt it?

[Zakal1]

The pressurestat in this machine is just a trigger which sends an on/off signal to a larger contactor. This contactor switches the elements on and off.
What can happen is the contactor fails to open completely and leaves some of the elements powered up constantly.

You can usually visually identify this fault as the contactor has a small tab in it which switches side to side when it operates. If the tab is not moving all the way to the side when it operates, it means it's bad. It could be moving all the way but have an internal fault which is keeping the elements on as well, the best way to check is to get the machine up to pressure, wait until the small pressurestat clicks, immediately power off and unplug the machine and check continuity across the contactor outputs.

The contactor is located next to the circuit boards under the drip tray area, it'll look something like this:



I can't remember where the best place to get them is, it was a fair while ago that I needed one. Coffeeparts may have them or you could try Jetblack Espresso as they have some Cimbali parts I think.

Hmm, interesting. I was starting to wonder whether another part was the culprit, other then the control board but wasnt sure if it was possible. But this seems like it could be a potential culprit, and likely a lot cheaper than replacing the ECB. I'll do some more testing and report back.

I just pulled the ECB out overnight and gave it a good clean with contact cleaner and put it back. Dunno if it will do anything, but this machine has poltergiests, so maybe it will just scare them away

[Zakal1]

So is it just supplying power to the element all the time and never switching it off, or is it switching it on and off but at the wrong times/ temps?

Yeah, basically the element is turning on when the power is turned on to the machine, and then never switching off until I kill the power after the overpressure valve gets triggered. It stays on the entire time despite the pressurestat clicking off.

[Javaphile]

Many of the parts in La Cimbali machines are standard off the shelf products that they've slapped their label on and jacked the price up through the roof.

If the problem in the contactor is with just the shunts/contact points and the coil is functioning properly take a look on fleabay for an overstock/extra/odd unit with the required number of shunts with the required carrying capacity and ignore what the triggering coil rating is. Then just swap the shunts/points out with yours as I did on mine. The coils weren't interchangeable, but the shunts/points were.


Java "Prefers to pay $5 rather than $200" phile

[prh]

I would be surprised if something compatible couldn't be sourced from any industry-oriented electrical component supplier - RS Components, Element 14, Mouser, etc.

[Javaphile]

You might find this thread helpful in sourcing a replacement part. A couple more pics of the contact points. When they get old one or more points can weld together causing the behavior you describe.


Java "Gotta love interchangeable parts." phile

[noidle22]

The pressurestat in this machine is just a trigger which sends an on/off signal to a larger contactor. This contactor switches the elements on and off.
What can happen is the contactor fails to open completely and leaves some of the elements powered up constantly.

You can usually visually identify this fault as the contactor has a small tab in it which switches side to side when it operates. If the tab is not moving all the way to the side when it operates, it means it's bad. It could be moving all the way but have an internal fault which is keeping the elements on as well, the best way to check is to get the machine up to pressure, wait until the small pressurestat clicks, immediately power off and unplug the machine and check continuity across the contactor outputs.

The contactor is located next to the circuit boards under the drip tray area, it'll look something like this:



I can't remember where the best place to get them is, it was a fair while ago that I needed one. Coffeeparts may have them or you could try Jetblack Espresso as they have some Cimbali parts I think.

[level3ninja]

So is it just supplying power to the element all the time and never switching it off, or is it switching it on and off but at the wrong times/ temps?

[Zakal1]

Quick update...I made an interesting discovery with the multimeter today:

1. When the power is off, and the boiler is cold, the switch on the pressurestat is in the "on" position, and the circuit between the two pins on top is closed. As you would expect.
2. As soon as power is turned on, the circuit opens despite the switch still being in the "on" position.
3. Once the boiler reaches pressure, the switch clicks into the "off" position (as it should), and the circuit remains open, but the boiler continues to heat up and increase in pressure.

So basically, I don't think the pressurestat is the problem. Somehow, the pressurestat is being bypassed the second power is supplied to the machine. Which unfortunately hints at the control board being the problem.

Does anyone have any ideas that would either be able to fix this or work around it? The control board is long since discontinued, and over $2k US from the one place that seems to sell it.

Any help would be greatly appreciated.

Let me know if any photos would assist.

[Zakal1]

Hi Guys,

I have a 2 group Cimbali M21 Plus, and its just started running into an overpressure problem.

My pressure gauge has never really worked properly and it now seems completely broken. I really should have fixed it long before now, but I haven't, and here we are. For that reason, I am not 100% certain the boiler is actually getting overpressure, but im about 95% sure that it is.

So basically, it turns on and starts to heat up as normal, and when it gets up to temp, the anti-vac valve closes and pressure starts to build, but after a while instead of just stabilising as normal, the boiler safey valve eventually starts to triger. It just sounds like a slow leak at first (and when i first heard it, i thought it was a leak and couldnt tell where it was coming from), but after a while it comes clear its venting out of the safety valve.

I have tried:-

1. Cleaning the autofill level probe (as a I read lots of people blaming overfilling for this issue) and even put a slightly sharper bend on it so it fills less.
2. Pulled out and cleaned (but did not replace) the water inlet solenoid and valve (i tested the solenoid by measuring resistance between the two pins and it showed some, i dont recall how much, but the article i read said that as long as it was not 0 or infinity, it was probably not the culprit)
3. Pulled out and cleaned and checked the operation of the pressure stat (and it seemed fine). Its one of the old Cimbali branded ones with a spring, like this: https://www.eunasa.com/en/article/vi...0_5bar_1_45bar

I cannot say for certain whether the pressurestat is clicking off or not, because once the anti-vac valve closes, i tend to move away to a safe distance just in case *this time* the safety valve fails. But what I can say is this:

1. when the machine is off and cold, the circuit is closed between the two pins on top of the pressure stat, as well as where both those wires (one whiite, one purple) plug into the control board.
2. When i manually lever the pressure stat "open", i hear the switch click, and there is no longer continuity between the two pins at the top, or the two wires at the control board (though there is continuity between each wire still (obviously).

So the pressurestat seems to operate as normal when everything is off. I cannot say for certain that the circuit is opening due to the boiler pressure or not, but i am ALMOST certain that it is. To my eyes, it looks like the angle of the lever is much higher than is needed for me to open it manually when im just levering it up.

So I think I have three potential problems:

1. The pressurestat is not working, and replacing it should fix it.
2. The pressurestat is working, but for some reason the element in the boiler is not turning off; or
3. Eveything else is working, but the safety valve is triggering too early (i really dont think its this).


First of all....can anyone thinkg of what else the problem could be?

Second, if its the pressurestat that needs replacing....which of the coffeeparts pressurestats can I replace it with, because it looks different to all of them?

Third, if its not the pressurestat, what else could it be?

Thanks guys. I am at my wits end, and not sure what else to try. Given these components are all quite expensive, I was hoping to get some ideas before i just start playing Part Replacement Roulette.

Thanks in advance.