Hi,

My Alex Duetto III is having a too high pump pressure when I am pulling a shot. It starts with 9/10 bar and then a new sequence starts and the pump pressure increases to 12 to 14 bar. Could the pump be defect? I have not tried to adjust the pump pressure as the pump seems to have two modes.

Very likely just needs the o-ring lubricated. If the o-ring is hard as rock, replace it.
(Talking about the o-ring inside the pump-bypass adjustment part of the pump, it's there to keep the pump from weeping out the breather hole, but when it gets sticky the valve stops being accurate).

At work, now... Can copy/paste pictures.
Part 18 is the o-ring in question, it goes around part 19.

Thank you! It fixed the problem

Hi,
I have an Alex PID machine. Your diagram is very helpful! I wonder if that O ring could be part of a problem I'm having with a lot of vibration when pulling a shot. this manifests as the pump needle oscillating a lot. The overall shot is ok. The problem seems to resolve after a decalc but swiftly returns.
I've scrutinised the pump and it appears to be functioning ok. Is removal reasonably straightforward? I'm concerned about knackering the pipework.
Finally, are replacement O rings easily available, and do they need to be heat resistant? any advice gratefully received.
cheers
Undrell

I'd check the expansion valve (aka OPV) first. On a rotary-pump machine, it should not be opening during brewing with the brew pressure set by the bypass valve on the pump.

undrell wrote:Hi,
I've scrutinised the pump and it appears to be functioning ok. Is removal reasonably straightforward? I'm concerned about knackering the pipework.
Finally, are replacement O rings easily available, and do they need to be heat resistant? any advice gratefully received.
cheers
Undrell

Removing "20" from the pump so that you can check and lubricate the o-ring is easy, yes.

I don't know about the availability of the o-ring on its own. I used to get them in kits that contained the spool as well, the kits are almost impossible to get ahold of now.
If you want to pay too much for it you could get the o-ring through Parts Town, it is part # 3370071362 if you want it by its "Schaerer number".
Schaerer 3370071362 O-Ring, Pump, 15 x 3, NBR 70, Black, Coffee Art Plus

https://www.partstown.com/schaerer/sh3370071362

It would be nearly free if purchased in bags of 50 (from a more reasonable source).

Thanks for all that! I'll start with the simple things first. I do have a spare OPV but I'll wait n see what emerges from the pressure valve first. I do have a reasonable array of O rings so I should be able to find something to fit.
Cheers
Undrell

ok. just taken the pressure adjusting valve out, very straightforward as you suggested. The O ring didn't look too bad so i applied some silicone grease and reassembled.. Lo and behold.. steady pressure gauge!! one small thing, which i hadn't paid much attention to, the pressure used to come up from around 4, to 9 bar just before the shot started. Now it's immediately at 6 bar on starting the pump.
great advice much appreciated. Cheers
Undrell