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La Marzocco Linea high dispensing pressures and constantly running procon water pump

Postby Melinda on Sat Sep 03, 2011 11:35 am

Hello,

I have a La Marzocco Linea AV two group machine at a small coffee shop. We have had some issues lately for the first time with our machine. The water pump was running all the time and it was getting hot. I replaced the pump which didn't fix the problem. The dispensing pressures are also too high. When running a shot it is about 9 then jumps up to 15 or greater shortly after that and sits there. There is no leaking from the expansion valve even when the boiler heating light comes on and the pressures are too high. I think it may be the expansion valvue but would this cause the pump to run all the time and get hot? It gets hot enough for the water line to the espresso machine to get hot also. Any suggestions would be appreciated!

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Postby duke-one on Sat Sep 03, 2011 1:28 pm

If the pressure gets to 15 the pressure regulator at the pump is not set right. The pump running all the time has got to be either the "brain box" is sending the signal for it to run or the relay/contactor is stuck closed. Replacing the pump won't fix that. Sounds like you will need someone with tech knowledge, not an easy do-it-yourself type problem (other then ajusting the pump pressure regulator).
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Postby another_jim on Sat Sep 03, 2011 2:04 pm

Kenneth is right. The pressure is because the bypass valve is out of adjustment or frozen. The pump is running because the controls are turning it on. This may be a fault in the brain box, or it could be due to two other things: a stuck steam boiler fill valve (i.e. the boiler is not refilling after you steam), or a faulty boiler level sensor (i.e the boiler is overfilling)

In any case, you should start with the pump running problem first. Turn off the machine entirely and check if the steam boiler is too low (bad solenoid), too high (either bad sensor or bad brain box), or just right (definitely bad brain box).
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Postby Melinda on Sat Sep 03, 2011 2:17 pm

Thank you for you suggestions and advise. I do have someone coming today but could it be the pump relay? (I was reading the technical manual troubleshooting section) The steam boiler water level appears to be normal. The pressure goes up when the heating light is on and then goes back down and sits at about 9-10 then goes back up again. The machine does make a "clunking" noise (not when the heating light is on). I just had the release valve on top of the boiler replaced because it seems to be stuck open and releasing steam when condensed on the bottom of the top panels and dripped on the wires and ruined the fuse (which also was replaced). Wow, I seem to be having more problems in this last week than ever. I love this machine, and learning more about it each day. :) I don't always like leaving my machine in the hands of someone else without being educated about what is going on. I've only found someone about 2 towns away that really knows my machine.
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Postby another_jim on Sat Sep 03, 2011 2:43 pm

Oops, yeah. A stuck relay will do it too.
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Postby duke-one on Sat Sep 03, 2011 5:00 pm

Melinda: That is the way to learn how things work, don't work and get fixed. Read what you can, watch and ask questions when a tech is working on what ever is giving trouble. Espresso machine, washer, dryer, furnace; there is always something to glean and over time you get an understanding of the electric and machinery world. Good Luck!!!
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Postby Melinda on Sun Sep 04, 2011 3:44 pm

I located a relay for a reasonable price. Is the relay located on the electrical board? I will have someone put it on when it comes in the mail. I ordered it from wholelattelove.com. (hope it's a reliable site).....
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kshanticoffee.com: we love to make things and we also love coffee
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Postby duke-one on Sun Sep 04, 2011 6:33 pm

Melinda: "Swapping out" parts without knowing which is at fault can at times fix a problem but it is not the recommended path to success or knowledge. Is the relay at fault? You won't learn much from doing it this way. What type of relay is it? Do you know how to safely access it and test it? W.L.Love is a well known site but most will not accept returns on electric parts. Relays certainly do fail and can do so in the closed condition either from mechanical fault or welded contacts. Is the relay getting the signal from the control box? If you can not answer these questions you are not yet ready to troubleshoot your machine. You could burn up new parts or worse. I'm not trying to discourage you but you need to know some basics to get at the root of the problem.
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Postby erics on Sun Sep 04, 2011 6:38 pm

Let's rest for a moment - perhaps I'm off the base.

Do both groupheads react the same? Are you simply using the manual brew button or are you trying all of the dose buttons?

That particular relay is, perhaps, in the espresso world, unique to LM and you really should have ordered the part from an LM distributor - here is a good source - http://www.espressoparts.com/ . To the best of my knowledge, WLL does not deal in LM machines or their parts. That specific relay may or may not be available as a replacement part - if LM owners were lucky, that relay would simply plug into a socket but that's wishful thinking.

Secondly, ditto what KDM said.

edit - Thirdly - here is the relay - if, in fact, that is the problem - http://www.marzoccoman.com/servlet/the-93/Pump-Relay-%28Relay%29/Detail
Skål,

Eric S.
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E-mail: erics at erols dot com
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Postby PaulTheRoaster on Sun Sep 04, 2011 9:06 pm

This happened to an old Linea at a coffee shop where I occasionally fix things: the problem was that the ancient insulation had broken on the wiring connectors at one of the brew switches (this was an EE machine), but only on the side that runs the pump.

It would be worth replacing or heat-shrinking ALL the connectors on the machine if they are not in good shape.
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