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Knight sensor two failure

Paul Rice
Paul Rice Member Posts: 1
Hey guys,

Check out page 66 of the I & O manual on the wiring diagram. Sensor 1 is the Outlet, Sensor 2 is the Inlet and Sensor 3 is the Flue.

Hope this helps.


  • Big Will
    Big Will Member Posts: 396
    I have a few

    Knight out there and this is the first problem I have had. It showed lockout sensor two open. This happened three times and every time it reset and ran fine. I have ohmed the sensor from the first connections to the last. It all reads as it should. Tech help said they had run into this before and it was the K5 loom connector on the main board. So I checked this and even gave the two pins for the sensor a slight tweak to make sure they made contact in the plug. The distribute rs tech. said to cut the little zip tie that holds the two sensor to their wells because this held the wire too close to the heat exchanger and causes friction/heat to short the sensor. The wire looked fine but I did it anyway. So has anyone else seen this on a Knight if so what did you do about it?It has run for about a week with no failures since I was their. Just looking for some piece of mind.
  • bobbyg_15
    bobbyg_15 Member Posts: 3
    I've seen it and heard about it

    I'd seen it before, and then Mark Eatherton addressed the issue here on "the Wall" months back. (Thanks Mark :-) It is the zip tie on the sensor/wire/well. I believe Mark said sometimes the zip tie would even squeeze the well, making it act funny.

    note: How did you figure out which sensor is #2. I always have a hard time finding it in the manuals. I thought it was in the "User's information manual" but quickly looked through all three manuals (User's, I&O, and Service)and couldn't find it. Is it Sensor 1-inlet, sensor 2-outlet???
  • paul_79
    paul_79 Member Posts: 91

    i had one knight boiler loose both 1 and 2 sensors within one year and it looked as if the zip tie was pulling on the wire at the well
  • Big Will
    Big Will Member Posts: 396

    did removing the zip ties fix it or did you have to replace the sensor as well.
  • bobbyg_15
    bobbyg_15 Member Posts: 3

    I keep a service book with all of my Knight stuff in it. My page 66 is a notes page (I&O manual Models 80-500, back page KB-i&o-01, CP-2M-08/05)

    If I use the most current I&O manual - is everything the same if I need information for the older units? Should I keep both older and newer I&O manuals in my service book or just newer?
  • bobbyg_15
    bobbyg_15 Member Posts: 3

    On the three cases I have had, only removing the zip ties corrected the problem. Hope this helps.
  • eluv8
    eluv8 Member Posts: 174
    lochinvar sensor problem

    I would recommend replacing the sensor, whenever you apply stress to wires to the point they are loosing continuity you should replace them. I would be concerned with the long term reliability of the sensor. Removing the zip tie allows the insulation to hold the wires back in contact but they are still broken and should be replaced. Especially if under warranty by the manufacture, which I think should be extended for this,after all it was their assembly line that over tightened the zip ties in the first place causing a return trip to the jobsite and a less than impressed homeowner. How hard is it to loop the sensor wire up a little before strapping down the sensor. I understand its intent but a small loop relieving stress would still hold the sensor in place and not break wires if the zip tie is too tight. If enough come back they might take the problem seriously.
  • bill garnett_2
    bill garnett_2 Member Posts: 21

    I have seen this fault-s2 is the return sensor and sometimes thru xpansion/contraction the circuit opens-you can use the supply sensor that comes with the boiler if you are not using to sense the supply-just don't zip tie as tite as greg gibbs
  • Kal Row
    Kal Row Member Posts: 1,520
    it can also be the big connector the main board...

    fill with Vaseline and reconnect,

  • How tight....

    IS Greg Gibbs?? I've always found him to be pretty loose with his help :-) (No inuendos implied)

  • Big Will
    Big Will Member Posts: 396
    that is a point that tech help wanted checked

    they felt that the connection might be loose. I tweaked the pins with needle nose pliers so they would bind in the plug just a bit. I have used a paste that looks like petroleum jelly that is made for cars for of road or wet use. never would have tried that though. I have it on the truck for gaskets and things too. Is this something you have done a lot with success?
  • Greg Gibbs
    Greg Gibbs Member Posts: 75

    you have to be loose, and at times you have to be tight.
    Kinda' like known' when to hold 'em or when to fold 'em.
  • Greg Gibbs
    Greg Gibbs Member Posts: 75

    The "paste that looks like petroleum jelly that is made for cars" you speak of, would be the best, if you choose to try it. I remember watching my Grandad apply a little "goop" to the points on his old Ford.
    This "goop" can still be found @ any Auto Parts Store.
    DO NOT USE VASILINE...it does have a small amout of H20
    in it, and may over time rust the contacts. -Greg
  • Kal Row
    Kal Row Member Posts: 1,520
    worked fine, and i needed it on the origonal knights...

    if you have a newer model it should not be a problem as they have changed the connector, then you need to go back to the sensor tie, though i have not seen this problem in a verry long time - and i install a ton of knights
This discussion has been closed.