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WMB-155C issues

TimmyLS Member Posts: 7
So my boiler quit (wmb-155c, NG) on the coldest night in a decade. But we survived, and it did too! It keeps throwing an error code A06 though, no flame, tries to start a few times but doesn't light and then a little gas smell and the error code flashes. I've changed the gas valve and venturi. It was never properly set up for combustion when it was installed maybe 3 years ago, so it had always started rough, think a kind of a sort of muted thudding sound whenever it would start... the burner plate has cracks in it and looks a little dented in places, likely because of the years of rough starting. I have that part coming too, heat exchanger is fine, not dirty or cracked. Blower sounds normal. Had some techs take a looks but couldn't get the combustion to stay in spec. It kept going wonky. Wondering your thoughts - would a burner in bad condition keep it from lighting?


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,068
    Was it not lighting or was there a flame that the sensor did not see? If the flame sensor circuit has dirty parts, or there is a bad ground connection from the control to the actual sensor location, then you may not be sensing the flame so the gas valve will close right away

    I believe that uses a spark to light the flame... is there a spark happening inside the combustion chamber? You can usually hear the buzz of the spark unless the boiler room is very noisy.

    Flame sensor and spark electrode is where I would look first

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • 109A_5
    109A_5 Member Posts: 1,387
    Hello @TimmyLS,

    Is the Ground Wire connected ??? It looks missing.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • Tim_D
    Tim_D Member Posts: 128
    The cracked burner will make it difficult to get the combustion in spec. Also, check all of the control parameters. If the installer didn't set up the combustion it is possible that they didn't set up the control as well.
  • TimmyLS
    TimmyLS Member Posts: 7
    Thank you all! Sorry for the belated response, I didn't realize I wouldn't be notified via email if someone replied. 

    I changed the burner plate which indeed made a world of difference and had someone with a combustion analyzer set it up. Its actually starting smoother than ever, and maintaining a flame etc. 

    BUT as often happens, a new issue has cropped up. I've set the CH temp to 170 but after a brief period of "medium" fire (indicated by the flame icon) the temp reaches 140ish and then the boiler goes into low fire and maintains something like 135 as it circulates water to baseboards. .. which is not enough to heat the house very well so the thermostats are constantly calling for heat and not reaching temp. I've checked the best I can for loose wiring... the sensors look like fairly simple things, ie not a lot to go wrong with them right? 

    It is a combi unit, and the domestic hot water side seems to function fine, it will get up to temp, though its a much lower temp.

    I will make sure to check back soon. Thank you all again.