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Baxi Combi 105 cutting out.

Discussion in 'Plumbing and Central Heating' started by andynet, 21 Jul 2008.

  1. andynet

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    Hi.
    I have enjoyed the forums here very much and hope that some of you clever folk can give me a clue on the following subject.
    We have a 5 year old Baxi combi 105 which has the annoying habit of cutting out, (usually when you are sat in the bath halfway through washing your hair). The 'Fault on Pump or Low System Pressure' light flashes. If you switch the selector switch off, then back on again a few seconds later the boiler resets fine and continues to work. This can happen a couple of times a day and is driving me dafter than I already am. The system pressure is currently 1.25 but increasing it to 2.5 doesn't appear to make any difference. The problem doesn't seem to be demand specific but does seem to occur more in summer than winter. I do vaguely remember some talk of the pcb,s being a bit dodgy on these models. Would it be worth replacing it? I could manage that, (Ex Leccy), but for anything on the gas side I would have to call someone out, but would like your diagnosis on this.

    Thanks. :confused:
     
  2. baxpoti

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    Check the auto air vent is open and working
     
  3. diverdee

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    sounds like a dodgey flow switch if u a sparkey check inside the boiler cover should be wiring diagram.shows you were the flow switch is ( the boiler cover not combustion cover )
     
  4. andynet

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    Thanks for that. I'll try those suggestions tomorrow and let you know if I have any luck. ;)
     
  5. andynet

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    Hi,

    Both suspects appear to be behaving correctly at the moment, BUT it hasn't faulted today, (yet). I did notice Baxpoti that the air vent is missing the top screw. Should it be in there for normal running?

    Andynet
     
  6. LUNAT

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    HI


    i would also keep HW diaphragm in mind as i have come across this before.HW diaphragm and HW sensor very common on these boilers.
     
  7. diverdee

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    the screw missing from the auto air vent makes no difference
     
  8. andynet

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    Just put the lid back on after monitoring faultless behaviour. Went to wash hands and..............Nothing. Arghhhhhhhhhhhhhhh! Thanks for the advice. I'll have a look at the diaphragm and sensor scenario tomorrow. Will I need an engineer for replacing them?
     
  9. diverdee

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    does it ever need resetting on ch mode?
     
  10. baxpoti

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    Meaning?
     
  11. andynet

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    Apologies - The 'Nothing' means that it had cut out again. Never noticed it occur in CH mode, although the house is so well insulated we only ever use CH a couple of times a year.
     
  12. baxpoti

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    symptons?
     
  13. timmy74

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    Secondary heat exchanger or main heat exchanger blocked with crap maybe.
     
  14. andynet

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    Symptoms same a s always: 'Fault on Pump or Low System Pressure' light flashing. To restart I set a tap running, switch selector to off, then back to HW and its running again. Currently occurring 1 to 3 times a day, depending on usage. Very frustrating! Seriously considering hand in pocket time. :confused:
     

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