Baxi 105e All LEDs Illuminated

Discussion in 'Plumbers' Talk' started by Missteque, Nov 10, 2017.

  1. Missteque

    Missteque New Member

    Have a problem with a Baxi 105e where all the upper LEDs (30deg-80deg) are on and none are flashing.
    The boiler will sometimes fire up but not all the time - both for water (DHW) and radiators (CH).
    I have seen the boiler fire up with the fan running, so the fan and APS has been proved to be O.K.
    When the boiler fires up it runs for a while then shuts off as though it has reached temperature which it has not.

    Can someone confirm that when the boiler is initially switched on with a CH demand that the fan should first run, which then causes the APS (via the PCB) to fire up the burners?

    Would a faulty Overheat thermostat cause the fan not to run, is this a simple on/off sensor as apposed to a thermister?

    Would a faulty Central Heating Temperature Sensor cause the fan not to run?

    Why are all the upper LEDs (30deg-80deg) on?

    Thanks
     
  2. harry zona

    harry zona New Member

    Howdy miss, the lights are on cos the burner is overheating, it's a circulation problem, maybe pump.expasion .airlock,blocked pipe or trv's siezed
     
  3. Hager the Horrible

    Hager the Horrible Active Member

    Fan always comes on before ignition. I used to have a Baxi 105e and had an issue where the DHW would keep cutting out (all LEDs lit as if max temp reached) before the water at the tap got hot. My issue turned out to be a partially blocked plate heat exchanger (slowed flow through it causing rapid local overheat). I removed it and flushed it out using a pressure washer then replaced it. It sorted that problem. I don't think my CH circuit was affected though as I believe the plate heat exchanger is only used when there is a call for DHW.
     
  4. The Teach

    The Teach Screwfix Select

    On your boiler (if not in a fault event) during a call for central heating or hot water,
    The boiler asks the therminstors and overheat for permission to proceed,if ok then
    The pump runs and proves its flow switch,
    That flow switch powers the fan,
    The fan runs and proves its aps,

    Then Ignition.
     
  5. Missteque

    Missteque New Member

    Thanks for all your replies.

    "The teach" - is the "Flow Switch" the same as the "Central Heating Pressure Differential Valve and Switch" as shown top left on page 36 of the manual and the "Hydraulic Differential Pressure Switch" as shown top right on page 37 of the "Installation and Servicing Instructions" manual?
    Because although there is mention of a "Flow Switch" in section 3.1.1 "With a demand for heating, the pump circulates water through the primary circuit. At a predetermined flow rate the central heating flow switch operates, initiating the ignition sequence". there is never a mention again of it anywhere else in the manual, or is it another switch?

    I can see the "DHW Pressure Differential Valve" operating when the hot tap is opened but the fan still does not run.

    Thanks in anticipation Baxi 105e P36 CHPDV.jpg
     
  6. The Teach

    The Teach Screwfix Select

    yes
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice