La Cimbali M29 Select dosing issue

Need help with equipment usage or want to share your latest discovery?
User avatar
berkinet

Postby berkinet » Aug 10, 2018, 4:43 am

I have recently started having a problem with the volumetric dosing on my M29 Select. The shot extraction starts, and then the machine seems to think the volume has been reached and clicks off and then immediately started delivery again. Kind of like a stutter. The problem occurs regardless of the presence or absence of coffee in the filter and happens on both groups. However, the problem is not consistent. Some days it is severe, other days no problem at all.

Any ideas what might be causing this? I can make and post a video next time it happens if that would help.

Thanks for any tips.

User avatar
civ

Postby civ » Aug 10, 2018, 7:51 am

Hello:
berkinet wrote:... a problem with the volumetric dosing on my M29 Select.
... like a stutter.
... regardless of the presence ...
... on both groups.
Any ideas what might be causing this?

I would think that the most probable cause would be a flowmeter malfuction ie: one of the ports clogged with scale build-up/oxidation (there may be a clogged filter screen), impeller wheel intermittingly sticking because of loose deposits or both.

Probably just needs a good clean-up.

Cheers,

CIV

User avatar
berkinet

Postby berkinet » Aug 11, 2018, 4:17 am

Thanks for the pointer to the flowmeter. Sounds right on... Given the machine is now 10 years old (we bought it new) it would surprise be if there wasn't such a problem.

User avatar
civ

Postby civ » Aug 11, 2018, 8:03 am

Hello:
berkinet wrote:Thanks for the pointer

You're welcome.

berkinet wrote:10 years old (we bought it new) ...

Ahh ...
It depends on how much use it has had, your water supply quality and how you have gone about it's maintenance.
As a commercial machine in a home environment it may be in pretty good shape as you (I think?) don't pull 100+ shots/group/day. =-)

As I posted to another HB member:
What you have is a very good quality and time proven commercial espresso machine ...
... in a home environment, it is still a commercial espresso machine and as such needs certain things done.



EDIT:
In my previous post I refer to a flowmeter but, being a two group machine, you have two of them.
Independently of the fact that they probably need a good cleaning, if this dosing issue you have affects both groups you may well have something blocking the water circuit upstream (ie: before the flowmeters).

In any case, you may want to look into other maintenance issues such as pump, valve, grouphead and boiler descaling/cleaning up.

There is a lot of info here at HB about all those aspects of espresso machines.
eg: La Cimbali M29 overhaul project

Cheers,

CIV

User avatar
kolu

Postby kolu » Aug 11, 2018, 1:54 pm

berkinet wrote:I have recently started having a problem with the volumetric dosing on my M29 Select. The shot extraction starts, and then the machine seems to think the volume has been reached and clicks off and then immediately started delivery again. Kind of like a stutter. The problem occurs regardless of the presence or absence of coffee in the filter and happens on both groups. However, the problem is not consistent. Some days it is severe, other days no problem at all.

Any ideas what might be causing this? I can make and post a video next time it happens if that would help.

Thanks for any tips.


please, video might be very helpful. but this sounds like main control board malfunction.

anyway - is pump running all the time? clicking 3 way valves? I would check the power applied to them (on main board terminals) - I've seen machines do that when the output triac on main board was dying, but it is quite uncommon to have the same issue on more than one group at time.
might be worth checking the power supplied to main board (transformer output, decoupling capacitors and generally the whole power supply side on the main board) and also anything that supply power to the solenoids/pump during the extraction.
but first of all, disconnect flow-meters and see what happens without them (machine should signalise no-flow after a while and keep pumping for quite a while).