Giotto Premium Plus (approx. 2009 model) turning off after 10-15mins

[Jonny]

Hello Coffee Snob experts out there,

I would be very appreciative of any advice you may have on the problem I am having with my Giotto Premium Plus (approx. 2009 model). I recently had an issue where it was over filling and thanks to advice on this forum, I resolved this by removing the overfill probe and removing scale build up.

However, it is now turning off after 10-15mins. It heats up as normal and the pressure gauge goes to around 1.4 bars of pressure. I can see that the heating element switches off at this point and then comes back on again at around 1.1 bars of pressure. I assume this is relatively normal cycling of the heating element to keep the boiler pressure within the correct range? I can't work out why it would turn off though after sitting idle for 10-15 mins. I can see that the green power light turns off and the pressure slowly drops back to zero.

For the time being I have a very limited window of opportunity between heating up to the correct temperature and pulling a shot before it powers off...quite frustrating!

Open to any ideas or suggestions and happy to provide any more details which may help to diagnose the issue. I have an electronics background and multimeter available so can do some tests if needed.

Thanks in advance!

[marke]

Jonny, when you removed the scale from the boiler level probe, did you also do a full descale of the machine?

Also, how scale up was the level probe?

[marke]

Just noticed that you have stated that the gauge ranges from 1.1 to 1.4, this seems a bit wide, the dead and should be narrower.

Probably a good place to start, if you feel confident is to check that all the connectors have a good clean connection.

[Jonny]

Hi Marke and thanks for your repsonse!, Yes, I did a full descale first which improved things slightly but I still had an occasional over fill. I then went the next step and removed the boiler level probe and cleaned it with steel wool. I actually couldn't see much scale build up but it hasn't over filled since. I will double check all connectors and ensure they have a good connection. Any specific connectors I should focus on that are more likely to cause this type of behaviour? Cheers, Jonny

[dumiya]

Sounds like a bit like my Premium that I upgraded to a hybrid Plus. My problem was the switch (not sure what they are called) that turns the boiler elements on and off in the electronic module was worn. I replaced the module and it has not missed a beat since. The module replacement might be best done by a technician as the wiring must be correct

[sprezzatura]

Sounds like a bad controller. If your thermal cut out isn't popping and the pstat is working there isn't a whole lot left to check unless some water is shorting something out.

[sprezzatura]

Unfortunately there's a mechanical relay in the controller that wears out on the heating element circuit and pump sometimes. Some people replace this relay. My soldering skills aren't very good so I don't replace these. But if you're electronics savvy it's possible - the Giotto controller is pretty basic: the h.e. circuit is the black wire on the high-voltage side. There are three mechanical relays inside. When you slide the PCB out of the cover it opens like a book.

[marke]

If you do a bit of a search on the forums, there is a guy who is offering a relay replacement service. Let me know if you can't find it and I'll try to dig it up for you.

[sprezzatura]

Have a look at the top of the boiler. You will see a thermostat with two male spade terminals. With the machine off and unplugged from the power point, remove the female terminals. With your DMM check for continuity across the thermostat. Pull gently up on the red reset plug and check for OL. Sometimes the bimetallic thermostat fails or corrosion causes a fault. A cheap repair compared to a new level/h.e. controller.

[sprezzatura]

After thinking about it some more and drinking a couple of beers, you might have a faulty pstat. The membrane may be worn out. The contacts carbonised. Turn off machine and unplug. Take a look at those contacts. Turn the pstat pressure down to 1.0 bar and see if the dead band gap decreases.

[dumiya]

My original pstat had a wide range of 2-3 bars. It was metal cased. I replaced it with an all black plastic one which has a narrower band. I still think it is going be a module replacement. I tried/replaced every thing else but ended up replacing the module.

[Jonny]

Have a look at the top of the boiler. You will see a thermostat with two male spade terminals. With the machine off and unplugged from the power point, remove the female terminals. With your DMM check for continuity across the thermostat. Pull gently up on the red reset plug and check for OL. Sometimes the bimetallic thermostat fails or corrosion causes a fault. A cheap repair compared to a new level/h.e. controller.

Hi Sprezzatura and thanks so much for your advice.

I found the two terminals on top of a small, black, round device with a red button on top. Sorry if this is silly question but is this called the pressurestat or thermostat?

As instructed, I turned the machine off and unplugged. I removed the two black terminals on top of the thermostat and measured the resistance which was around 20 ohms. When I pulled the red button up it went to open circuit (O/C). Is this a good sign?

The contacts looked pretty clean but I gave them a further clean just in case. I then plugged the two black plugs back in and turned the machine on. I measured around 2 ohms resistance across the two terminals when I first turned the machine on. The resistance then varies between 1 ohm and 2 ohms during the normal operating cycle (i.e. as the pressure varies between approx. 1.2 - 1.4 bars).

After around 15 minutes, as normal the machine turned itself off (and the power light went off) and the pressure slowly dropped back to zero. At this point the resistance on the thermostat was around 1.5 ohms. Not sure if that helps :-(

Anyway, I'll try turning the pressure down to 1 bar as suggested and see what that reveals.

Update - after turning the pressure down to between 1.1 - 1.3 bar the same thing happened although it appeared to take a bit longer to occur. I'll try turning it down a little more to see what effect it has.

[Jonny]

Thanks for your response Dumiya. It's fantastic having some options to consider! Are you referring to the mechanical relay that Sprezzatura mentions below? Just trying to narrow down the next thing to check. Also, did you replace it yourself and if so, was it relatively straight forward?

[Jonny]

My original pstat had a wide range of 2-3 bars. It was metal cased. I replaced it with an all black plastic one which has a narrower band. I still think it is going be a module replacement. I tried/replaced every thing else but ended up replacing the module.

Mine is the black plastic one.

[Jonny]

Sounds like a bad controller. If your thermal cut out isn't popping and the pstat is working there isn't a whole lot left to check unless some water is shorting something out.

I don't believe the thermal cutout is tripping for two reasons:

1.) the resistance across the two thermostat remains at around 1-2 ohms when the machine switches off
2.) when I pull one of the connectors off to simulate an open circuit, the heating element turns off but the power light remains on (when the issue that I have experienced occurs, the power light goes off also).

So I'm guessing it's sounding more like a bad controller.