Question about Aprilaire 600 Humidifier

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Aprilaire 600 humidifier solonoid valve chattering in sync with d10 led

I turned on my furnace today and heard a noise from the basement.  It turns out it is the humidifer and it appears to be coming from the actual control panel in increase or decrease the humidity level.  When I turn the dial completely off - a led inside the panel labeled D10 flashes.  If I turn the humidity on - it chatters - in sync with what I believe is the solonid valve.  I disconnected power to the solonoid valve and it still flashes but does not click.  I took apart the solonod valve and inspected it, but it seems ok.

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  • mjbeeler Nov 17, 2007

    I have an Aprilaire 700 humidifier relay chattering. There's no call for heat on the system, but the relay is chattering and the D10 LED is flashing at the same rate - any ideas what is wrong?

  • rstpeter Nov 23, 2007

    I installed Aprilaire 600 two years ago. This week when I turned furnace on, I found the same problem as you guys described above. Is any one can help with this? The problem is control panel or solenoid?


  • Anonymous Jan 02, 2008

    I have the same exact problem as the two previously mentioned. We have had our 600 since 2002 and have had no problems until this past fall.

  • jasonsimms Nov 23, 2008

    Same problem here.  The red LED on the inside of the control panels chatters at the same rate as the what I think is the solenoid.  If I put it on test, it kinda goes away.  Put it on normal setting and it chatters.  Water is flowing during all of this, however.  I'll keep poking around....

  • kingofbytes Nov 23, 2008

    I have the exact same problem except this is with the Aprilaire Model 400 unit. Exact same problem. "Test" works with no problems. Turning it off shows D10 red light blinking. Properly turning it on yields the clicking noise. I will purchase the MFG#: 56 Humidifier control for $84 at IAQsource and see if that works.

  • foscaldo58 Jan 18, 2009

    I have the same problem on my Aprilaire 600 unit. I took a shot and replaced solenoid and it was wrong. The new solinoid is doing the same chattering when on. I am going to buy a new control panel as that seems to be the only thing left to replace.



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I fixed my problem by ordering a new control unit (model 56) from IAQSOURCE. Installing the control unit took a few mintues, and once the new control module was installed, I've had no more problems. The URL is as follows:

Posted on Jan 22, 2008

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I have exactly the same problem and the only thing that helps is to turn the control to "off" for several hours, then turn it back on to a low setting (2 or 3). This helps for a few weeks before the problem comes back.

Posted on Jan 20, 2008


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1 Answer

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