Glow Worm 18HXi

Discussion in 'Plumbers' Talk' started by NT555, Nov 3, 2017.

  1. NT555

    NT555 Member

    Hi All,

    Firstly, I'm not a plumber.

    Management pushed me to disconnect an upstairs rad and flush it. After reconnecting it the boiler would not start correctly. The fan would spin up and then it would click off, then repeat. I realised it wasn't happy so turned off the system. I re-checked the system for air (there wasn't any)and the only valves I turned off/on were the TRV and lockshield either side of the rad.

    I then turned the system back on but got no signs of life from the boiler. The boiler has a bi coloured LED (Red/Green) and a liquid crystal display that shows errors, or in normal working conditions the temperature. Anyway, no signs of life.

    The connector panel below the boiler has 240V on the supply line and the adjacent connector has 240V when it gets demand from the controller.

    On the PCB the fuse is fine and the 240V is getting to the PCB via the main double pole switch on the front panel. I carefully removed the PCB and looked it over. A couple of the electrolytic capacitors were mildly bulging but apart from that it looked fine with no signs of heat or dry joints.

    The ******* annoying thing is that prior to me flushing the rad the system has been fine and without any issues.

    Any advise would be most welcome.

  2. terrymac

    terrymac Well-Known Member

    Did you use a multimeter to establish voltage between line and neutral is 240 volts ? ( at the boiler terminal block ) ?
  3. Well, when the fan on my 30CXi started pulsing - revving up and then down repeatedly - everyone diagnosed a faulty PCB. Which it was. And, as you suspect, the components that go are almost always the electrolytic capacitors.

    If the display is otherwise dead - and no F code - that would also suggest the same.

    Are you up to replacing them as a trial?!

    Here's a more comprehensive list of possibilities, covering all sorts of loose connection possibilities.

    http://vaillantgroup.intellirespons...XI / HXI / BG330: Pulsing Fan / Blank Display

    Anyhoo, I suspect the removed rad was purely coincidental.
  4. NT555

    NT555 Member

    Many thanks for your help chaps.

    I removed the PCB and did some tests on the bench. It appears that the main incoming transformer is open circuit on the primary side.

    I've found a new replacement PCB online for £120 delivered. Hopefully it should sort the problem..

    I'll report back. Thanks again.
    Deleted member 33931 likes this.
  5. Nice work :)

    Wow - faulty trannie? That must be a bit more unusual, I'd have thought.

    Fingers crossed for a fix.
  6. NT555

    NT555 Member

    Hi All, Happy Days!! Fixed!!!

    I found the following thread which made me take a second look:

    I replaced the open circuit transformer and two electrolytic capacitors within the switch-mode PSU part of the board and it works!! The replacement transformer came from an old laptop PSU and the caps were in my stock.

    I checked the capacitance of the removed caps and they were roughly half their stated values. With the PCB living so close to the heat of the combustion chamber it's not surprising that they failed. Interestingly the caps were not high temp rated. Not good for Glow Worm business I guess...

    Anyway all sorted.

    Sincere thanks to you all.

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