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Intermittent pilot ignition control - replacing cable/wires?

newdognewtricks
newdognewtricks Member Posts: 11
in Gas Heating
Hello,

Is it possible to buy intermittent ignition board cables without buying an entirely new control board? My Dunkirk boiler has developed a habit of not firing the main burner, but working again if I unplug and replug the combination PV, MV, MV/PV cable that connects to the gas valve. I feel like the whole IPI isn’t shot, there’s just a bad connection in that particular wire, and I could solve the issue if I just replaced the little 3 pronged combo cable.



For reference this is a UTECH 1003-600A.

Let me know what you think. Thanks!

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,750
    If those are regular spade connectors, you could probably cut that plug off and crimp new connectors on. Or try cleaning and tweaking the existing.

    I don't know if that wiring harness is a Dunkirk part or a Utec part. You could probably do a little searching and find out. Start with the boiler manual.
    newdognewtricks
  • mattmia2
    mattmia2 Member Posts: 8,364
    I would be a lot more suspicious of where the terminal solders to the board than the terminal on the wire.
    newdognewtricks
  • newdognewtricks
    newdognewtricks Member Posts: 11
    edited May 2022
    mattmia2 said:
    I would be a lot more suspicious of where the terminal solders to the board than the terminal on the wire.
    Any idea why the main valve would lose power randomly from a bad connection then get it again after a replug?

    @EBEBRATT-Ed I am hesitant to do much work myself as I’m a complete newbie and I’ve already spent $1,000+ throwing parts and labor at this thing throughout my HVAC company’s troubleshooting. If I messed something up I’d be pissed. What’s my risk here? What can I break if I try this myself? It seems like my tech would tell me I have to replace the whole board anyway…

    Thanks guys, appreciate the help.
  • mattmia2
    mattmia2 Member Posts: 8,364
    Are there any errors flashing(does this board even have any diagnostics?)?

    Does the pilot valve light then the main valve not turn on or does the pilot valve fail too?

    Find the instructions for this module for a more specific sequence but I think this control works by:

    Start spark and open pilot valve
    Prove pilot with flame rectification
    If flame is proven, open main valve.

    If it isn't proving flame which I think it is doing through flame rectification through the spark probe, it won't open the MV.

    It needs a good ground path to the pilot burner to get a good current on the flame rectification sensing. You could be jarring something in to better contact when you unplug and plug back in the connector. Or it could be a bad connection in the board itself either for the MV or something else.
  • Jamie Hall
    Jamie Hall Member Posts: 21,503
    "Any idea why the main valve would lose power randomly from a bad connection then get it again after a replug?"

    That is quite exactly what I would expect it to do if there were a bad connection pretty much anywhere in the signal path. It might be a damaged wire. It might be, as @mattmia2 sigguested a bad solder joint at the plug. The most likely point, however, are the plugs and sockets themselves, or spade connectors. Plugs and sockets -- particularly the Molex sort, which you may have - -are notorious for developing intermittent bad connection problems. Replacing the plug or socket -- or the entire harness -- may help, but only if you ensure that the mating socket or plug is absolutely clean and tight and free of corrosion. Spade connectors are easier to clean and free from corrosion -- but in both cases what you are looking for is the connection to not only be physically tight (wiggle is not an option!) but bright metal.

    The same would apply to any other ground path connections.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Dave Carpentier
    Dave Carpentier Member Posts: 543
    If you reterminate the wires, dont forget to label them (MV, MV/PV, PV).
    If its the board side, Ive had to repair bad solder joints on many electronics (but not hvac). Its always where something is pushed on to a connection.. the joint starts to weaken and then goes open at the circuit board. The action of you unplugging and plugging in the connector wiggles it and solves it temporarily. That unit might be sealed and inaccessible to re-flow the joints though.
    30+ yrs in telecom outside plant.
    Currently in building maintenance.
  • mattmia2
    mattmia2 Member Posts: 8,364
    The terminals have a lot more mass than the other components and frequently don't get heated adequately when the board is wave soldered.
    Dave Carpentier
  • newdognewtricks
    newdognewtricks Member Posts: 11
    edited May 2022
    mattmia2 said:
    Are there any errors flashing(does this board even have any diagnostics?)? Does the pilot valve light then the main valve not turn on or does the pilot valve fail too? Find the instructions for this module for a more specific sequence but I think this control works by: Start spark and open pilot valve Prove pilot with flame rectification If flame is proven, open main valve. If it isn't proving flame which I think it is doing through flame rectification through the spark probe, it won't open the MV. It needs a good ground path to the pilot burner to get a good current on the flame rectification sensing. You could be jarring something in to better contact when you unplug and plug back in the connector. Or it could be a bad connection in the board itself either for the MV or something else.
    No diagnostics on the board unfortunately. The PV always works fine, the problem seems to be limited to the MV.

    Now I’m wondering if the issue is the flame sensor - or lack thereof. As you can see in the original picture there is no connection to the SENS male spade. However there is a black female spade connected to the main valve, and a female spade just sort of floating in air next to the control board. I wonder if a tech took it out at some point and forgot to plug it back in?

    Jamie Hall said:
    Spade connectors are easier to clean and free from corrosion -- but in both cases what you are looking for is the connection to not only be physically tight (wiggle is not an option!) but bright metal. The same would apply to any other ground path connections.
    There is definitely a lot of wiggle in the male/female spade connection.


  • mattmia2
    mattmia2 Member Posts: 8,364
    Is that unconnected wire just connected to a screw on the body of the gas valve? If so it is probably for burner ground.

    The pilot valve will open regardless, then it sparks, then if it proves flame it opens the main valve. It will probably close the pilot valve after some timeout if it doesn't sense flame but you would need the instructions for that control to figure that out.
  • newdognewtricks
    newdognewtricks Member Posts: 11
    Yes it is connected to a screw on the gas valve.

    It’s a 5s time out but I don’t think I’ve ever seen/heard it time out. It always just seems like the pilot stays on and is available, but the main valve never opens.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,750
    If he (service tech) left a wire off call the service manager and **** him out. You should not be paying $$$$$$ for a system that won't work...................especially if they can't diagnose the problem
  • Dave Carpentier
    Dave Carpentier Member Posts: 543
    On a wiggly female spade connector, you can sometimes give the "hoops" on the edges a bit of a squeeze to tighten it up. Squeeze a bit, test, repeat. If you go to far, use a small flat blade to pry it back open a bit.
    30+ yrs in telecom outside plant.
    Currently in building maintenance.
    MikeAmann
  • newdognewtricks
    newdognewtricks Member Posts: 11
    Thanks for your comments everyone, I appreciate the help.

    Do I have any options if the problem is the board's solder? Or would I have to just buy a whole new board? What about the terminals on the gas valve itself?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,750
    @newdognewtricks

    if it's the board you would have to replace it. The terminals on the gas valve can be scraped and cleaned. I thought you said it was the connections at the board that are the problem?
  • newdognewtricks
    newdognewtricks Member Posts: 11
    Just did some troubleshooting and have some interesting updates.

    1) The boiler does not start working again if you simply turn it off and on - you have to somehow break the circuit with the board.
    2) I can actually get it to start working if I only unplug and replug the cable that connects to the gas valve - the other side of it (that connects to the board) can stay plugged in, along with the 24V cables.

    Thoughts?

    Thanks all.
  • mattmia2
    mattmia2 Member Posts: 8,364
    edited May 2022
    try plugging that gas valve ground wire in to the burner ground terminal. Sounds more like you are making a poor ground connection to the pilot burner better when you disturb things.

    Also look very carefully at all of the spark wire to see if it is chaffed or burned and shorting to the cabinet somewhere.
  • newdognewtricks
    newdognewtricks Member Posts: 11
    edited May 2022
    mattmia2 said:
    try plugging that gas valve ground wire in to the burner ground terminal. Sounds more like you are making a poor ground connection to the pilot burner better when you disturb things. Also look very carefully at all of the spark wire to see if it is chaffed or burned and shorting to the cabinet somewhere.
    Really? That spade doesn’t have an insulated cover. It doesn’t look like it’s been used.

    Spark wire looks good as new.

    Ground connection and terminals on valve:

  • mattmia2
    mattmia2 Member Posts: 8,364
    It gives the current through the pilot flame a more direct path from the electrode back to the control to detect the pilot flame.
  • newdognewtricks
    newdognewtricks Member Posts: 11
    edited May 2022
    The plot thickens…turned off the boiler, unplugged everything from the board besides the spark. That’s MV/PV/MVPV, 24V, and 24V GRND. Yet the pilot is still lit. That has never happened. Normally once I pull the MV/PV/MVPV off the gas valve the pilot turns off.

    Plugged everything back in and turned the boiler back on - now it doesn’t light the main flame.

    What the heck is going on?

    PS this is without connecting the burner ground. I was about to do that before this latest development.
  • mattmia2
    mattmia2 Member Posts: 8,364
    24vac between mv/pv and pv from the control should be what opens the pilot valve. do you smell gas with it off?

    You have the grouped connector unplugged completely and the pilot burner is still burning?
  • newdognewtricks
    newdognewtricks Member Posts: 11
    Nope, no gas smell. Just a boiler with apparently zero electricity and no cables besides the spark plugged in, but still with a lit pilot.
  • newdognewtricks
    newdognewtricks Member Posts: 11
    Maybe it’s more accurate to say the pilot never shut off after the main valve stopped firing. It was working earlier after the trusty unplug/re-plug.
  • newdognewtricks
    newdognewtricks Member Posts: 11
    Lol. Did the same old operation again and the pilot turned off.

    Do all boilers taunt you like this or is mine just haunted? 
  • mattmia2
    mattmia2 Member Posts: 8,364
    put a voltmeter on the main valve terminals. the valve might be bad. see if there is 24vac between the mv/pv and mv when the main burner won't fire.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,019
    Have you tried placing this black wire on this terminal?
    Before you do... check that the terminal is labeled (GRD). Either Burner (Grd). or 24V (Grd). GRD stands for Ground
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    MikeAmann

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