Baxi 105HE flue/fan fault ??

Discussion in 'Plumbing and Central Heating' started by robpegs, 20 Apr 2007.

  1. robpegs

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    Baxi 105HE fan or flue fault?

    Hi all, ok I have a Baxi 105he with a fan or flue fault light on, this started intermittently and got worse until a full failer, i have changed the APS and this fixed the fault for all of two hour. i have checked for blocked Venturi,all APS pipes are fine. the boiler is again working intermittently.
    the boiler is about 18 months old. and had no other fault until now, im guessing the PCB,any other things i can check before going down the new PCB route.
    Regards
    and are the pcb on these models prone to fail? and if so what parts ,dry joints etc
     
  2. ChrisR

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    Common problem, pcb 5112380 which replaced 248074. The old board had several faults, don't bother trying to repair it.

    You'll probably find if you look carefully enough , that when it goes "wrong" and flashes the 50 light, the fan gets a tiny kick.
     
  3. robpegs

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    hi, thanks for the reply, interesting about the pcb. looks like no option but to replace pcb, by the way the fan runs fine with no problems at all, before and after it fires up, strange how the new aps worked for a hour or so, at some points the heating can be running fine , and when it switches to dhw, it dies with the same error, and visa versa.
    thanks for the new model number for the pcb as well.
     
  4. robpegs

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    i see a few boilers use this pcb, a user has a new one on ebay , but it's from a different boiler (Potterton), could i use this pcb as they have the same part number
    regards
    rob
     
  5. ChrisR

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    Baxi = Potterton.
    Changed a board on one of these on Thursday, and it worked fine.
    "But I just changed the board" he said.
    "Where did you get it" I said
    "ebay", he said.
    "What did you do with the old board" I said
    "I put it on ebay " he said.

    But if the fan actually runs it isn't the #1 standard fault. Could be a real air flow fault! Lots of things to check all corgi things really.
     
  6. baxpoti

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    Dodgy ebay APS?
     
  7. robpegs

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    sorry ,APS was new from part center not ebay!!
    but good point about the pcb on ebay!!
     
  8. spikeymikey1980

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    FYI. I recently began experiencing the same fault symptoms as described on this post, however I managed to fix the problem and i'd like to share my experience here.

    My problem was as follows:

    My boiler (Baxi 105HE) developed an intermittent Fan/Flue fault (i.e. 50degree LED blinking). Occasionally the boiler would work correctly and I would get hot water but the problem gradually got worse until every demand for hot water resulted in the fault.

    Having removed the outer and inner case from the boiler the first thing I checked was the APS. I used a multimeter to check for continuity between the 'normally-closed' and 'common' contacts of the APS micro-switch. These had a resistance of about 400 ohms when closed: way too high!

    I then turned on the hot water to create a demand and probed the 'normally-open' and 'common' contacts for continuity. The fan turned on and these should have had near-zero resistance as the venturi could be heard to activate the APS switch however these were in fact still open-circuit.

    My conclusion: Dirty APS micro-switch contacts.

    The solution:

    I removed the APS from the boiler and carefully drilled out the rivets holding the micro-switch to the main APS body.

    I then removed the micro-switch from the APS body and used a Stanley knife to gently prise open the two halves of the switch. I removed each leg of the switch in turn at which point it became obvious that arcing of the contacts through repeated switch activations had blackened the tips of the contacts.

    I cleaned all of the contacts with fine wire-wool and re-assembled the switch.

    I checked for correct switch operation with my multi-meter before fixing the switch back to the APS. As I previously drilled out the rivets I used 2x M2 bolts and nuts to re-fix the switch.

    Finally, I screwed the APS back into the boiler, re-connected the two air tubes and the switch wires and turned the boiler back on.

    Et voila! The boiler now works repeatedly and consistently.
     
  9. namsag

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    9 quid for switch would have been far easier
     
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  10. Trouble666

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    Lol at Namsag! Yup, a new Switch, would've saved all the hassle!
     
  11. spikeymikey1980

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    I needed hot water ASAP hence the micro-switch surgery!
     
  12. gasgas

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    Thats what I like to see Spikey! A bit of initiative. £9 for a switch is trivia in boiler repair terms but if it took you 30 minutes and you are a minimum wage earner then that is equivalent to over three hours pay. Clearly as you have intelligence you are not a minimum wage earner though. If you had called me in as a Gas Safe Registered engineer the cost would have been £60 plus the cost of an APS complete. But then it costs me £100 a week just to be legally able to work on boilers, before I go out the front door and start the van.
     
  13. mysteryman

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    Have you checked the calibration of the switch?
     
  14. namsag

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    Check the date of the post ?? ;)

    100 Quid to step out the door you need to address your overheads no need for them to be this high.
     
  15. gasgas

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    Namsag- yes I did notice the date of the post. What brought me there was a search for a part number on google and I just started reading it and thought well done, I wouldn't bother breaking open a microswitch, but as a long time research engineer in electronic products I know the satisfaction one would get from fixing something - which if it is burnt out contact points in a switch means that the switch is not correctly specified for the job.
    My £100 guess is a little high, as you suspect. It is for the week, not each time I step out the door. To be accurate, I am sure you are familiar with these numbers:
    Annual GSR fee £200
    Annual CIPHE fee £100
    Annual pub liability insurance £400
    Loss of earnings every 5 years having to do reassessment: £1000 / 5 = £200 p.a.
    Cost of reassessment every 5 years £1000 / 5 = £200 p.a.
    Owning a van - well that depends if you have leased one at £300 a month or bought an old banger that owes you nothing.

    OK so assuming my van is the latter type and owes me nothing, van insurance, tax and MOT is £14 a week
    So adding this lot up, that is £36 a week. Sorry, you are right. Unless you have a leased van in which case you can easily add £80 a week to the costs.
    I am currently having an apparent minor disagreement with my gas agency who expect me to drive to one job 37 miles away (74 return, two hours travel time across minor roads) and service a boiler, for a reward of £19. sorry, I wont do it. Send me 6 jobs in one postcode that is within 15 miles of where I live, and I will do it.
     

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