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Thread: Malfunctioning group solenoid?

  1. #1
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    Malfunctioning group solenoid?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    My old Bezzera BZ99s group solenoid no longer seems to be working properly and while it pulls shots just fine, the pressure isnt released after pumping stops and it will do PF sneezes if I dont wait long enough for the pressure to bleed out past the puck.

    I have tried removing the solenoid valve to check that the hose to the drip try is clear and also that the solenoid is group to dump path is clear - I can easily blow air through both paths while I cannot blow air through the solenoid from the boiler inlet side.

    I also measured the voltage across the live and neutral leads and confirmed that while the pump switch is on, there is mains voltage present plus I tried pumping with the live and neutral leads disconnected the from the solenoid and found no water pumping through in this case.

    Finally, I do get water flowing through the solenoid to the drip try after I pump very briefly with a blind filter installed (so that there is only low pressure in the group) but not if I pump for more than a second or so.

    None of this has changed after disassembling an reassembling the solenoid (its a T body type, not the flat plate type) and checking that nothing inside it jammed; nor has backflushing with Cafetta (with very brief pumping bursts) made any difference.

    It seems the fault is the solenoid valve but it there any way that I can service it (it is the "T" type valve, not a flat base one) or do I just have to admit defeat and buy a new solenoid?

    Greg

  2. #2
    Senior Member Koffee_Kosmo's Avatar
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    Re: Malfunctioning group solenoid?

    All I can think of as a possible solution

    Take the 3 way valve apart and clean
    Check the associated hoses or pipes are clear as well

    Brass parts [especially the small ones] may need a sand with the finest wet/dry sanding paper available

    KK



  3. #3
    A_M
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    Re: Malfunctioning group solenoid?

    Quote Originally Posted by 202A2A252A2C2E4B0 link=1270513629/0#0 date=1270513629
    I also measured the voltage across the live and neutral leads and confirmed that while the pump switch is on, there is mains voltage present plus I tried pumping with the live and neutral leads disconnected the from the solenoid and found no water pumping through in this case.
    DANGEROUS... Working live... NOT RECOMMENDED for no Qualified persons.....

    Step one.

    The simple way and the safe way..

    Disconnect from the wall FIRST.

    1: Then measure the coil resistance ? * Should be a few hundred ohms etc Ohms *NOT Open Circuit.? *

    If OC.. Dead coil.. *Some have a OT fuse internally.. *Does not matter dead = Replace.

    2: You have already done this... Supply of voltage..

    But there are ways to do it better...

    Get a voltage pen... Cheep and very effective. No need to *start sticking probes in...

    VOLTSTICK NON CONTACT VOLTAGE TESTER approx $20 - Worth ya life... YOU BET. Great for checking walls when you go to drill as well. Would have been a great tool for roof insulators. But no one thinks around here any more.

    They have the ability to sence.. Thus hold *close and when the item is powered etc will light. *SAFE and Good.

    3: Lets say good coil.. And Power.. *If ya not hearing the solenoid click as it get pulled into position... Sticky slug... Personal problem. Maintenance.


    4: If all that is good.. Then you have a blockage some where.. Personal problem. Maintenance.


    Now... Lets visit that again *8-)

    DO NOT GO STICKING PROBES etc inside a live machine; when you do not have to, or are not Qualified.

    For Gawd sake.. PEOPLE. * Work safe.. PLAY safe.




  4. #4
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    Re: Malfunctioning group solenoid?

    any other solenoid you can swap within the machine, maybe an auto fill one?

    just to test them swap back

    you geting any click clicks at all?


  5. #5
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    Re: Malfunctioning group solenoid?

    Thanks for all of the safety warnings, AngerManagement. Being an electrical engineer, I do have some sense of the dangers involved with working with live mains voltage and rest assured, I do take lots of precautions before doing ANY tests with the cover off my machine. I do NOT recommend that people with no working knowledge of electrical systems perform these sorts of test.

    Now, given that I have done what I stated, in regard to checking the pathways with air + disassembly and all of the electrical checks, IS THERE ANYTHING I CAN DO BESIDES REPLACE THE SOLENOID?
    The problem appears to be that it is jamming in the pumping position while there is high pressure in the boiler to group path.

    I guess I worded things unclearly before when I stated that "I tried pumping with the live and neutral leads disconnected the from the solenoid and found no water pumping through in this case". By this, I meant that no water pumps though to the group with the solenoid leads disconnected (it all gets routed back to the tank via the OPV). Water pumps through to the group just fine with the solenoid fully wired up (hence the machine can still pull shots, albeit with PF sneezes).

    Im thinking that my only course of action left at this point is to try soaking the disassembled solenoid, minus the coil, in Cafetta for a while and then if this doesnt work, I will need to bite the bullet and buy a new group solenoid. :-/

    Greg

  6. #6
    A_M
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    Re: Malfunctioning group solenoid?

    Quote Originally Posted by 414B4B444B4D4F2A0 link=1270513629/4#4 date=1270518102
    Being an electrical engineer, I do have some sense of the dangers involved with working with live mains voltage and rest assured, I do take lots of precautions before doing ANY tests with the cover off my machine. I do NOT recommend that people with no working knowledge of electrical systems perform these sorts of test.
    No problem... But while it is now clear that you have some understanding ;) I guess the issue may also be for thos reading and thinking they can do the same :o

    Voltstick is a great tool for those lurking 8-)


    What was teh coil reading... I am being anal ;D

    If the standard check look OK.. And firing when should - only two things I can think of.

    1: Pull apart and soak and clean...

    Inspect all parts under a good light. If the coil is good and getting voltage... Then the other issue is just mechanical... Spring and or a bit of crap causing it to jam ???

    2: Something else is not firing at the time you expect... and thus the path is not as expected.

    Have a BZ99 in my shed and all teh ccts.. Have to go out for 30min. Will get back and do some checking.. That valve is a right little pain and the soft tubing going back to the inlet side... Have had the check valve in there cause me issue with head flow and OP dumping......

    PM me and may be we can do a live chat :o

  7. #7
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    Re: Malfunctioning group solenoid?

    pm sent

  8. #8
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    Re: Malfunctioning group solenoid?

    Greg,

    you wrote

    Quote Originally Posted by 646E6E616E686A0F0 link=1270513629/4#4 date=1270518102
    /.......IS THERE ANYTHING I CAN DO BESIDES REPLACE THE SOLENOID?.................

    ...............Im thinking that my only course of action left at this point is to try soaking the disassembled solenoid, minus the coil, in Cafetta for a while and then if this doesnt work, I will need to bite the bullet and buy a new group solenoid. :-/..........

    It is as you have stated. Disassemble and clean, reassemble and test.

    If this doesnt work, replace with new valve assembly.

    Coils usually either work, or they dont, so if the valve is obviously clicking, then the fault will lie in a clogged or worn slug assembly. Doubt you can buy one without the other (ie just a coiul, or just a valve assembly sans coil).

    Excise the offending part from the machine and spend money. The more you procrastinate, the longer your baby is off the road.

    A.

  9. #9
    A_M
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    Re: Malfunctioning group solenoid?

    Quote Originally Posted by 7B4F584E55627E525B5B58583D0 link=1270513629/7#7 date=1270533482
    Greg,

    you wrote

    Quote Originally Posted by 646E6E616E686A0F0 link=1270513629/4#4 date=1270518102
    /.......IS THERE ANYTHING I CAN DO BESIDES REPLACE THE SOLENOID?.................

    ...............Im thinking that my only course of action left at this point is to try soaking the disassembled solenoid, minus the coil, in Cafetta for a while and then if this doesnt work, I will need to bite the bullet and buy a new group solenoid. :-/..........

    It is as you have stated. Disassemble and clean, reassemble and test.

    If this doesnt work, replace with new valve assembly.

    Coils usually either work, or they dont, so if the valve is obviously clicking, then the fault will lie in a clogged or worn slug assembly. *Doubt you can buy one without the other (ie just a coiul, or just a valve assembly sans coil).

    Excise the offending part from the machine and spend money. The more you procrastinate, the longer your baby is off the road.

    A.
    Coffee parts... Coil on its own.. And I should think so.... The main part never fails unless some body gets over zealous.


    http://www.coffeeparts.com/bezerra/bezerra-spare-parts-1.html

  10. #10
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    Re: Malfunctioning group solenoid?

    Heck, I started with a Gaggia Carezza so I know how to handle machines without a group solenoid :).

    The machine still works but its just not at its best. *:-?

    Coffeeparts only sells the body for the flat plate version (already checked that before starting this thread) so Id have to buy the whole thing. Plus the T version costs more than the flat plate one (and I have a working spare flat plate solenoid from an old Gaggia) :-/ Ill probably just get it from Barazi to make sure I get the right unit (since the CoffeeParts listing for the BZ99 shows the flat plate version).
    Unless someone here can categorically state that the CoffeeParts solenoid 300046-22 http://www.coffeeparts.com/misc/solenoids.html does fit the BZ99.

    Given that it does switch (see previous reference to operation with solenoid electrically disconnected), Id say they assembly is worn enough to jam when there is back pressure from the group. It seems OK when I disassemble it but I guess the high pressure means the tolerances needed are pretty fine. *:(

  11. #11
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    Re: Malfunctioning group solenoid?

    i had one a while ago that a little spring on the little slug was rusted and was effecting it.

    if i remember right after soaking in lots of different stuff, WD40, oil caffetto etc etc i think i grabbed a metal skewer and paper clip and just pulled / eased the spring "apart" it then seemed to operate fine....

    not sure what brand it was but worth a look if you have it apart

    edit found a pic, this spring the one inside the channel not the outside one

    Leeham

  12. #12
    A_M
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    Re: Malfunctioning group solenoid?

    Quote Originally Posted by 3D313835353C500 link=1270513629/10#10 date=1270537904
    i had one a while ago that a little spring on the little slug was rusted and was effecting it.

    if i remember right after soaking in lots of different stuff, WD40, oil caffetto etc etc i think i grabbed a metal skewer and paper clip and just pulled / eased the spring "apart" it then seemed to operate fine....

    not sure what brand it was but worth a look if you have it apart

    edit found a pic, this spring the one inside the channel not the outside one

    Leeham
    That is a sick slug... Ya know that slug bait is not good for ya ;D :D ;)

  13. #13
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    Re: Malfunctioning group solenoid?

    Quote Originally Posted by 4E424B46464F230 link=1270513629/10#10 date=1270537904
    edit found a pic, this spring the one inside the channel not the outside one

    Leeham
    Id say thats it!!!! :D
    Thanks, Leeham - I fiddled with that a bit but wasnt sure that the inner spring was meant to move much. :o
    Now for the machione to cool down.....

    Greg

  14. #14
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    Re: Malfunctioning group solenoid?

    its been a while since i looked at that thing, I am sure (95 %) the "spring" stretched out a fair bit more than it is in this pic.

    anyway, thought it might help

    let us know how you go


  15. #15
    A_M
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    Re: Malfunctioning group solenoid?

    Quote Originally Posted by 3D373738373133560 link=1270513629/12#12 date=1270589179
    Quote Originally Posted by 4E424B46464F230 link=1270513629/10#10 date=1270537904
    edit found a pic, this spring the one inside the channel not the outside one

    Leeham
    Id say thats it!!!! *:D
    Thanks, Leeham - I fiddled with that a bit but wasnt sure that the inner spring was meant to move much. *:o
    Now for the machione to cool down.....

    Greg
    If yours looks like that with the inner spring.. Then that will be it.

    The outer spring is to move the slug back to a home position. *The inner spring has a seat on both ends and that is what seal when the slug moves to either position. *

    If the seat is not clearly visable at either end.. The ya have a problem as the slug can not seal.

    The spring is to give the seal some movement and allow for excess pressures and a flow path..

    Again, I dont often see this as I just pull down and soak and put in an ultra sonic bath. *I also flex the springs as a standard process; thus an automatic process. *Hence like many automatic behaviours when try to explain how one does something the important bit may never be actually said. *Its only when some one audits your work and processes that they identify that missing bit of info.

    Opps Quality comes into it again

    Let us know how ya go.

  16. #16
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    Re: Malfunctioning group solenoid?

    Well I tried moving the spring about with a skewer and it moves ok but the problem remains :-/. Mine has a much shorter groove so I could only wriggle it a bit.

    Ill give it a blast in a friends sonic cleaner but Im not hopeful

    Greg

  17. #17
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    Re: Malfunctioning group solenoid?

    Quote Originally Posted by 717B7B747B7D7F1A0 link=1270513629/15#15 date=1270811458
    Well I tried moving the spring about with a skewer and it moves ok but the problem remains :-/. Mine has a much shorter groove so I could only wriggle it a bit.

    Ill give it a blast in a friends sonic cleaner but Im not hopeful

    Greg
    That inner spring should be expanded such that the seal at either end is flush... If it is compressed... Then that suggests a fault with the spring / slug.




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