This just started recently -- machine is about 15 months old, MP version. Occasionally when the timer comes on in the morning the boiler will fill/top up (this is normal). However, over the last couple of weeks it will occasionally choke as if there is something blocking the hose in the reservoir. The first time I noticed this I woke up to the "Time Out Alarm Boiler Filling Up" error and it was following a backflush routine with detergent. I will then turn off and back on (sometimes 2-3 times) to get the boiler to fill normally.

Machine is run off the reservoir with a mixture of distilled (or Zero Water) and regular filtered water to add some hardness. Everything else functions normally (machine heats, pulls shots, steams, etc exactly as before).

Any idea what the issue could be? Would rather not bring it in for service if I can avoid it.

I believe the GS3 has the same part as a GB5. There is a mixing block for the preheating function that is susceptible to blockage due to scale. This is typically the first thing to indicate there scale since the orifice which water passes thru is much smaller than you would ever imagine. If you are handy, call La Marzocco and ask for tech support. They are amazing and will walk you through it. Ive never found a person up there that didn't know exactly what to do.

Update on this -- took the machine to a place that services LM machines. I had originally intended to drop it off and leave it, but the guy who was there (owner perhaps? not the tech guy) played with it for a bit. Same symptom occurred initially, but we ran it quite a few times and put quite a bit of water through it and had the boiler refill itself. The problem seemed to go away....he didn't think it was scale or a blockage -- he felt it was some sort of vapor lock happening (although he's not the tech unfortunately).

Took it home and it functioned properly for just under a week and then started acting up again (same issues happening)....boiler choked on fill the other day and today when cleaning the group after pulling a shot it was almost as if the air bubble made its way there....pressure dropped, water flow stopped. Ran water from the tap, boiler refilled properly, and everything seemed to be ok again. Will see if it works itself out I run more water through it.

It appears to be the same issue that lifeis11 had back last year so I PM'd him but haven't heard back yet...he may have the answer!

If it fills up in the morning it is the steam boiler.

If water is not getting to the steam boiler, it is either an intermittent solenoid or bad check valve that decides to stay closed (rather unlikely - AFAIK they have a propensity to fail open). Since the pump is pushing water at 9 bar or so, and the steam boiler is at 1.5 or so, I don't think a simple vapor lock will prevent it from working. Also, since you are always able to pull shots, I don't believe the reservoir hose is blocked.

In fact, since you say you turn it on and off and after 2-3 times it works, I would probably be very suspicious of the solenoid.

I would check this out quickly since your pump and motor are working against some blockage which may cause damage over time. Just my tuppence.

Just saw the reply now. I was under the impression that the 'morning boiler fill' was actually the coffee boiler (the pressure gauge for the coffee boiler will jump slightly after the fill).

I do occasionally get a 'choking' issue when attempting to pull a shot, so not really sure what the issue is. I'm hoping it might somehow have something to do with the need to replace the o-rings in the group....someone had mentioned that this can produce really strange symptoms in some cases (I now have a replacement set, so am going to give that a go).

I've managed to find 2 instances of people "on the internet" who seem to have had a similar problem. One is on HB, but did not respond to my PM and did not post the solution in the original thread (bummer). The other is on a German(?) site....and Google translate seems to indicate the issue was a bad pump in that instance.

What's most frustrating is that it doesn't happen all of the time.....but just when it hasn't happened for a while and I think it is working correctly, it happens again!

Coffee boiler does not have a fill level sensor since it is always, 100% full.

I assume you are using it with a reservoir. If it happens both on coffee pull and boiler fill, then I would guess it to be the reservoir hose. It might be bent in a way which pull it shut when the pump pulls water through it, or there may be something in the reservoir that blocks the opening.

Just my tuppence.

It is being run off the reservoir (which is clear/clean, as is the hose). I've tried to see if there is something causing a 'kink' but can't see anything that might be doing this. Go figure.

I originally assumed it was the steam boiler filling, but can't understand why the pressure gauge for the coffee boiler jumps slightly when the morning 'fill' happens. Anyway -- again, the last 2 days it's been fine again. Strange.

Still need to do the o-ring replacement....not sure it will make any difference (or why it would), but given the machine is almost 1.5 years old, it's probably due anyway.

mixedup wrote:I originally assumed it was the steam boiler filling, but can't understand why the pressure gauge for the coffee boiler jumps slightly when the morning 'fill' happens. Anyway -- again, the last 2 days it's been fine again. Strange.

The change you see in coffee boiler pressure is normal when the steam boiler is autofilling. I'm not sure about the cause, but here are my two theories:

1. The coffee boiler doesn't have a fill solenoid, so it's always connected to the output of the pump. When the steam boiler autofill solenoid opens, both boilers are connected to the output of the pump. But since the coffee boiler is essentially closed and there's no resistance in the path to the steam boiler, the water goes to the steam boiler. But there's probably a slight increase or decrease in pressure seen by the coffee boiler gauge when the solenoid opens.

2. The coffe boiler heat exchanger that's used for pre-warming the input water runs through the steam boiler. When cold water enters the steam boiler, the temperature of the water in the HX decreases, resulting in a change of pressure in the coffee boiler.

I think it's #1, or maybe #1 and #2, but maybe Bill Crossland can give us the skinny.