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I need an expert.

This is a crazy one. Slant fin 100 series gas boiler. The boiler went out last week. This is what has been replaced so far.
Gas ignition module, circulator pump, damp vent. The new damp vent doesn’t want to work. The ONLY way to get this thing fired up is if I jump the harness to the vent damp. I can get the boiler to kick on but it will not shut down. I have to shut it down at the switch. I’m jumping #2 black and #3 white yellow and that is the only combination that will work. I had a guy here 3 times and every time he’s left the boiler was running but after awhile it shuts down and I can’t get it to fire up unless I jump it. I should mention that I have to jump it at the female harness that plugs into the damp vent itself. It won’t work if I jump it at the damp harness on the aqua stat. My guy has been doing boilers for over 20 years and even he’s saying “I just don’t get it” Any and all help is greatly appreciated. Thank you fellas.


  • Keith M
    Keith M Member Posts: 78
    Have your contractor call Slant/Fin Technical Service at 516 484 2600 between 9am and 5pm EST. He needs to have his electric multi-meter available and be by the boiler.
    Thank you,
    Keith Muhlmeister
    Slant/Fin Corporation
  • Ironman
    Ironman Member Posts: 7,062
    Not to be unkind, but does anyone there have a digital meter and understand how to logically diagnose circuitry?

    It sounds like nothing but parts changing is going on in hopes that you'll land on the correct spot. The problem with that is that another one may have been created in the process.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Tim McElwain
    Tim McElwain Member Posts: 4,553
    What Make and Model relay do you have on your boiler? It could be a problem with the vent damper connection as we have had some problems with those operating intermittently.
  • GW
    GW Member Posts: 4,592
    The cable may be bad, the boiler control may be bad. I would gently jiggle the board terminal and or press and prod the board gently to see if I can get the flame to drop out
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • GW
    GW Member Posts: 4,592
    Ok I Re read, there are issues, perhaps you need another heat guy.

    The new damper is bad or the damper simply isn’t getting the correct signal.

    Jumping the harness means you may be bypassing the thermostat call
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • Henry
    Henry Member Posts: 995
    You need a certified licensed person to work on a gas appliance and not somebody jumping this and that!
  • JohnNY
    JohnNY Member Posts: 3,052
    The change-parts-until-it-works method is still around, I see.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Plumbing in NYC or in NJ.
    Take his class.
    JUGHNE Member Posts: 10,278
    I danced with a vent damper, HSI and Flame sensor and finally the real culprit showed up. It was the gas valve. HW Smartvalve.

    Intermittent failure, changed valve and HSI/FS (+15 years old) and now good.

    Many things are not immediately obvious, 3 trips to catch the gas valve actually not opening.
  • Lance
    Lance Member Posts: 241
    Sadly this outcome is becoming typical. Glad problem resolved. Can't find a problem until the boiler tells you where to look and you know how to hear it. We see more sophistication, complication in what used to be simple controls all for what? Confusion and higher repair bills and more intermittent occurrences often the hardest to find. Many manufacturers of units fail to properly verify quality of parts from their vendors. No one knows until the customer cries help! By the way who is making all the failed stuff we find? We are worried about illegals what about bad parts? If enough bad parts come into the country doesn't it make sense we will have more problems?
    Principles never change.