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Baxi 5111603 PCB Replacement Kit

Discussion in 'Plumbing and Central Heating' started by stewc, 1 Sep 2021.

  1. stewc

    stewc

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    Hi,

    I have had the wiring replaced on my Suprima 40L with the Baxi 5111603 PCB replacement kit. It works for a while, 30mins to an hour before it locks out. I'm pretty sure its overheating.
    Anyway I checked the fault code as per the manual (hold reset button for 10s, then count red flashes) but I'm getting 2 fault codes that don't appear in the user manual. These are

    1. Goes straight to lock out, slow flash of red led, 3s on, 3s off.
    2. Or, after holding reset button, 8 flashes within 10s.

    As I said, neither of these fault codes are in the manual, only 2 and 5 flashes. I have been in touch with Baxi technical help and they don't know what the fault codes are either.

    I was wondering if anyone else has come across these two faults and might know what they mean.

    Thanks

    Stewart
     
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  3. DP

    DP

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    Boiler could be overheating for many reasons. Would it not be better to investigate that than worry about the fault code?
     
  4. stewc

    stewc

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    I have, this is my point, I was hoping the fault code could give me a better insight in to what was wrong.

    I've change the PCB, wiring, thermistor, overheat stat, pump, got as much air out the system as I can, bled the radiators. Can't see what else I can check.
     
  5. Gasguru

    Gasguru

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    Is it on S plan...is the bypass opening sufficiently on the pump overrun?
    How old is the pcb...AFAIR the newer design is just as hopeless as the original board.
    There's a few other checks and another part that could be on the way out but they're combustion related and non diy.
     
  6. Agile

    Agile

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    I have to say that I have experienced few failures on the new design of PCB.

    The old PCB used to have a lot of bad solder joints develop and could often be resoldered to get them working again.

    Sometimes the temperature sensors were unreliable.
     
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  8. MeldrewsMate

    MeldrewsMate

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    What is the temperature difference across the flow and feturn when the boiler is running?
    I've had to deal with occasional heat exchanger blockages on Suprimas, usually on the larger output models; this will lead to excessive temperature differences (high delta T).
    If it comes to needing a new hex, I'd urge you to consider a new and more efficient boiler.
     
  9. Agile

    Agile

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    Stewart, the OP has not posted for over a week.

    So Stewart, this new PCB was it brand new in a sealed manufacturer's box?

    Or was it from an open box or was it from a "so called" reconditioned source on ebay?
     
  10. stewc

    stewc

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    Ordered another new pcb, fitted this and still the same problem. Check flow and return temps just before it stops and these are 55 and 45 degrees.. I'm guessing its new boiler time
     
  11. Agile

    Agile

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    I would never give up.

    But I have to say that none of the things mentioned gives me any strong clue as to what is wrong.

    However, if I was in front of the boiler then I would be doing some further operational tests to try to find out the cause of the problem.

    These boilers are somewhat susceptible to overheating and so I would be doing some tests to investigate that further. Including investigating timings to see what the boiler parameters are at the instant of lockout.

    But for safety reasons I cannot give details on an open forum.

    I would also question how you have measured the flow and return temperatures!
     
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