I've been troubleshooting my humidifier for a bit now (just learning this stuff as I go). It would appear the wiring for the furnace (apparently the transformer) meets the wiring for the humidistat and the solenoid inside the furnace. I've replaced the solenoid already as we have hard water and it's pretty easy to replace.

What I'm seeing is that when I pull the new solenoid out of the wiring junction, I get a solid 28v at the wiring junction. When I put the solenoid back in, I get nothing. That doesn't make sense to me. If they are all wired together, where's the voltage going?

  • 1
    I'm not sure if this is the answer but there won't be any voltage at the solenoid unless the furnace is on and the humidastat is calling for moisture. THEN the solenoid valve will be powered and water will run to the humidifier. Feb 19, 2020 at 15:19
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    ...and with it disconnected there might be stray voltage (at essentially no power) that you are measuring with a meter, but that would simply be grounded by the coil, but not operate it nor stay at 24-28V without power to back it up...
    – Ecnerwal
    Feb 19, 2020 at 16:23
  • Thanks Steve. That makes sense, but I have the humidity setting on the humidistat cranked with the furnace running and get no voltage. I took some additional steps to hopefully illustrate what's going on. - turned on humidifier, checked voltage with all connected: 0v -pulled the solenoid off while furnace still running: 24v -turned off humidifier, reattached solenoid :0v (expected) -turned on humidifier with attached solenoid: 0v
    – Chris
    Feb 19, 2020 at 16:30
  • If you can add a sketch, or photos (even better) of the wiring at the furnace terminal block, thermostat, humidistat, and humidifier we may be able to understand the situation better.
    – Greg Hill
    Feb 19, 2020 at 16:36
  • <img src="i.ibb.co/YkH4mkc/IMG-2213.jpg"> <img src="i.ibb.co/cT1SLRL/IMG-2484.jpg"> <img src="i.ibb.co/xqKF6DM/IMG-5059.jpg"> <img src="i.ibb.co/vmvxz2H/IMG-6232.jpg"> I still don't understand what's going on but that transformer certainly doesn't look so good in the last pic.
    – Chris
    Feb 19, 2020 at 16:45


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