I haven't contacted them because they're in a different country and I thought it wasn't worth the trouble.

I guess I could clean the wires but can't see how that would change anything, as they look in perfect shape and not dirty at all.
What do you mean by "wiring diagram"? I'm not very knowledgeable when it comes to this kind of things

mammamia wrote:Hello Musica. First did you contact store you bought it? 6 month is surely within warranty period. If you want to fix this yourself then here we go. Before replacing anything did you try to clean and rewire original wires? Many times bad connectors or connections cause faulty behavior. Pull wires out, give a good clean and rewire them would be a good and easy start. Brass wire brush or green scrubby is recommended to deal with those terminals.

Second It would be good to find wiring diagram to fully diagnose symptoms at your end. Someday you would be out of warranty and you better know your machine. From here you can get better understanding and effective approach with someone having similar experiences past. (I tried to find diagram for ten mins and failed but you may success to find it or acquire it from dealer)

Third I would not like to talk about Control board(or box) here yet. Dealing with faulty controller is another story. So I pause here.

This is HB. Great people(not me ) wait to help you. Thank you for reading long post. Pls take your time, be safe and let us know your progress.

In my time doing repairs I've had far more pressurestats fail than relays on control boards.

Step 1 is to swap out the pstat, and if that doesn't work then I'd move toward the controller. Boyt can repair a control board cheap: https://boytenterprises.com/

These little Mater pressurestats can go after 6 months for sure. I've replaced many of them. I've also used Boyt a few times. Let us know how it works out.

Nick

Just changed the pressurestat for a new Mater. The machine heated up to 1.2 bar then stopped. So far so good. But 30 seconds later, the pressure had already dropped to 1.0. Heater kicks in again and this time doesn't stop until the pressure gauge reads 1.6. I switched off the machine at this point.

What do you think?... I've reproduced this twice.What may be causing this pattern?

Yours is wired so that the relay inside the controller does the heavy load switching of the element and only a small current goes through the pressurestat. This arrangement does make it a little more likely to fail in the controller relay rather than the pressurestat. And now that you've changed the pressurestat and the overheating problem persists that makes it fairly conclusive that it's a controller problem.

However, there is one other thing not involving the controller nor the pressurestat that can in theory cause your symptom: a bad scale clog or other obstruction in the pipe leading to the pressurestat. Not likely in your case since it looked so squeaky clean, and also this generally causes a consistent rather than intermittent overheat symptom. To be 100% sure you might remove the pipe from the T fitting and try snaking a flexible steel wire like a guitar string through it and/or give it a descaler soak.

That controller should not have failed in only 6 months use. You might try contacting the shop where you bought it and see if they might send you a replacement. Be sure to tell them your overheating symptom, that the pipe is clean, and that you tried a new pStat.

nicholasnumbers wrote:Boyt can repair a control board cheap: https://boytenterprises.com/

That's a good option that I've used a couple times. Not only can he repair them he can test and confirm that it was indeed a controller problem. Not sure if that's a convenient option for Europeans, or if there is someone closer to your home that does the same sort of repair work.

One thing I should mention; what model pressurestat did you get? Direct replacement? They make different models with different band variances. I.e. 0-1.2 bar or 1-2.5 bar. Just want to make sure you have the screw adjusted properly so you're operating in a good range.

If it's still acting up then it's time to move to the controller. Bummer you're having this issue but it's awesome you're willing to try to repair it yourself!

Nick

nicholasnumbers wrote:what model pressurestat did you get? Direct replacement? They make different models with different band variances. I.e. 0-1.2 bar or 1-2.5 bar.

Yes, it's the same. What's weird is that the first time around it stops at 1.2 (so that's an indication it's calibrated properly), and only then does it go all the way up to 1.6+

Bummer you're having this issue but it's awesome you're willing to try to repair it yourself!

I've got no choice! Just shipping the damn thing back to the people I bought it from would be $200+!

One thing that puzzles me is why can't the machine hold the pressure once it's reached 1.2? Why does it go down so quickly?

PS: just to sum up, I'm dealing so far with 3 problems: 1) heating element fails to switch on when pressure is low; 2) heating element fails to switch off when pressure too high; 3) pressure drops quickly.

Do you think a failing control box could explain all three issues?

musica wrote:Do you think a failing control box could explain all three issues?

It would not explain ' 3) pressure drops quickly '. That is often due to a leaking anti-vac valve. Listen closely for a faint hiss there, or an occasional hiss like the sound of a water droplet on a hot stove. You can sometimes detect a leak with the help of an inspection mirror, looking for places where the steam fogs the mirror. But if you do this be sure to unplug the machine before getting in there with the mirror.

A sticking pressurestat switch or mechanism is often the cause of both 1 and 2. But in your case I think you saw the same issue in both the old and in a new pressurestat, which makes that a less likely culprit. A bad relay or other defect in the controller also could explain both 1 and 2. Your symptom, that the relay sometimes opens as expected at 1.2 bar, then begins to fail to open is I think a little uncommon.

P.S.
Just to be clear, when you say it sometimes goes to 1.6+, are you are saying that it's increasing and you play it safe at that point and turn off the machine. This would be indicative of either 1) the pressurestat failing to open (clog in pipe or sticky mechanism) or 2) a relay in the controller failing to open (a bad relay, or failing to properly sense and react to the pressurestat circuit).

homeburrero wrote:It would not explain ' 3) pressure drops quickly '. That is often due to a leaking anti-vac valve. Listen closely for a faint hiss there, or an occasional hiss like the sound of a water droplet on a hot stove. You can sometimes detect a leak with the help of an inspection mirror, looking for places where the steam fogs the mirror. But if you do this be sure to unplug the machine before getting in there with the mirror.

It doesn't seem to be leaking. But when I switch on the machine, while the pressure is still at 0 and it starts heating up, the breaker valve does let out some steam for about 5 seconds. I don't know why, but it happens each and every time I turn the machine on.

A sticking pressurestat switch or mechanism is often the cause of both 1 and 2. But in your case I think you saw the same issue in both the old and in a new pressurestat, which makes that a less likely culprit.

Yes, exactly the same symptoms with both pressurestats.

Just to be clear, when you say it sometimes goes to 1.6+, are you are saying that it's increasing and you play it safe at that point and turn off the machine. This would be indicative of either 1) the pressurestat failing to open (clog in pipe or sticky mechanism) or 2) a relay in the controller failing to open (a bad relay, or failing to properly sense and react to the pressurestat circuit).

That's what I mean, yes. At 2 bar, the breaker valve starts screaming.

musica wrote:It doesn't seem to be leaking. But when I switch on the machine, while the pressure is still at 0 and it starts heating up, the breaker valve does let out some steam for about 5 seconds. I don't know why, but it happens each and every time I turn the machine on.

That's how it's supposed to work. These valves not only prevent a vacuum when the boiler cools, they also are designed to vent off air from inside the boiler when the machine first heats up.

musica wrote:That's what I mean, yes. At 2 bar, the breaker valve starts screaming.

That's consistent with either the pStat or controller relay staying closed when it should be opening the circuit. BTW it's the pressure safety valve that opens in this case. (The vacuum breaker opens at low pressure and the safety valve opens at high pressure.)