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Weil Mclain Ultra 105 - b25 code

bleeblee Posts: 4Member
I recently did a maintenance kit on my Ultra 105,
About a day or two later I started getting a b25 error message. It came and went, but every few days it showed up more frequently over the course of the last 2 weeks. Now I woke up this morning and the boiler wont stay on for more than a few minutes and is constantly showing the b25 code

Any ideas?
I'm a newbie, so I don't know any technical terms or abbreviations


  • bleeblee Posts: 4Member
    (This is what I've found so far in the Weil Mclain Manual)


    Instructions in this supplement are based
    on factory default parameter settings.

    [Display flashes 9, then b in first position; last two digits on steady (code)]

    Outlet water temp rose too quickly - burner off for 10 minute wait (burner recycles, increasing wait 1 minute each attempt, to a max of 15 minutes)

    1 - Possible hot water return from DHW tank.
    2- Make sure system does not have trapped air preventing proper flow.
    3 - Inspect and verify system piping and components.
    4 - Verify piping agrees with boiler manual recommendations.
    5 - Verify proper circulator(s) operation.
    6 - Possible loose connector on boiler outlet sensor. Tighten connector.
    7 - Possible bad boiler supply outlet sensor
  • bleeblee Posts: 4Member
    edited January 9
    Another thing I noticed, when doing the maintenance kit, the cover plate that is supposed to be torqued to 50 inch lbs was hand tight. I took 7 of the 10 nuts off by hand which was kind of odd. When I re-installed the cover plate I torqued them to 50 inch lbs
  • bleeblee Posts: 4Member
    Now it is throwing an E 36 code as well

    "Outlet water temperature sensor open circuit"

    1. Inspect outlet water temperature sensor and wiring.
    -Replace sensor if wiring correct and in good condition.
    -Replace low voltage wiring harness if problem persists.
    -Replace control module if harness replacement doesn’t resolve
  • DZoroDZoro Posts: 756Member
    Make sure all the connections that may have been disconnected are back in their proper places.
    Especially those two sensor wires.
  • Tom_133Tom_133 Posts: 619Member
    You probably broke the supply sensor, easy to do. They are cheap and available. Oh and you dont need to drain they just screw in.
    Montpelier Vt
  • HVACNUTHVACNUT Posts: 2,125Member
    New sensors should have come with the maintenance kit. If it worked before you worked on it, then Occam's razor.
  • GWGW Posts: 3,399Member
    HVACNUT said:

    New sensors should have come with the maintenance kit. If it worked before you worked on it, then Occam's razor.

    what may I ask is Occam's razor?

    This is always a fine line-------"it worked before you came to do the maintenance...."
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • Tom_133Tom_133 Posts: 619Member

    I have never seen the sensors come in any kit. I could be wrong though happens all the time.

    383-500-300 thats the supply and return sensor part number.
    Montpelier Vt
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