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Weil McLain CGT draft inducer issue

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Skypilot
Skypilot Member Posts: 4
I have a Weil McLain CGT 2nd generation(with relay) and the draft inducer will not spin up and therefor will not continue the sequence. I have several of these boiler in operation for more than a decade and am quite familiar with them.
Simply...
Draft inducer does not spin up and circulator is live.
Disconnected inducer connector from IBC to test.
No power coming from connector at IBC and neutral is live.
Jumped power into inducer wiring pigtail at the connector... inducer startup was normal without hesitation or noise.
No other high side power issues found.

Ok... must be a bad IBC. Replaced IBC with board from adjacent working boiler.
Nope...nada...same

IBC 1107=1
Green power light...yes
Red Tsat/Circ light...yes
no flashing lights

Thanks for your consideration

Comments

  • HomerJSmith
    HomerJSmith Member Posts: 2,511
    edited July 2023
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    It can't be the board because of the substitution. It can't be the connection wiring to the IDM from the board because of the jumping.
    The board isn't sending power to the IDM. Look at any negative pressure switch, wiring and tubing. Jump the mico switch contacts. Also, take a paper clip and clean out the tubing connection port on the IDM, making sure the port is not obstructed with exhaust debris. Hope this helps.
  • Skypilot
    Skypilot Member Posts: 4
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    I don't believe there is any pressure switch operations prior in to the IDM firing. The only pressure switch involved would be after IDM fires for proof of vent to allow the start up sequence to continue. Vent and tubing are confirmed to be clear.
    Thanks for the reply!
  • HomerJSmith
    HomerJSmith Member Posts: 2,511
    edited July 2023
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    Yes, that's true. Just making sure that everything is ok. IDM s have low starting torque. Some IDMs have a cooling fan in the motor housing that is visible and can be started by starting the spin with a pencil or such. Some IDMs can be lubricated with oil on the bearings ports at each end of the motor.

    Measure the voltage at the board where the IDM power comes from with the IDM disconnected. 110V? You said, no. The relay isn't delivering power to the IDM. What do you mean that the neutral is live? Did you check the line polarity coming into the appliance?
  • Skypilot
    Skypilot Member Posts: 4
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    Problem solved...
    Long story short it was the TFE switch(Proof of Flame). Continuity tested multiple times with wire attached... all good. Removed wires and found sporadic continuity.

    Cause was failed solder connection at TFE terminal therefor IBC could not continue sequence to initiate IDM.

    Thank you Homer and all who contribute to these boards! We all have some knowledge to offer... and we are all better for it. Keep posting!