Stuck on debugging Aprilaire 600 after reading many other threads

Old 01-18-18, 08:09 AM
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Stuck on debugging Aprilaire 600 after reading many other threads

Other threads on this type of humidifier were really useful in determining what did and didn't work, but I'm conceding defeat and asking for help. It's on an Amana gas furnace that was originally installed in 2008.

Short version: I've verified vs the wiring diagram included with the controller, replaced the temperature probe, and the solenoid does start water flowing if I bridge the H terminals. Test mode does not trip the solenoid.

The long version: The control unit failed a few years ago and was replaced under warranty. At the end of winter it stopped working again (out of warranty). The folks doing the annual spring tuneup looked at it but did not resolve the issue. This winter we had someone out again and they tried replacing the controller again, but guessed that unit was bad as well. They offered to order one (for $300) and come out again to replace it. I ordered a unit myself and reconnected the wires in the same spots with before/after pictures. The only change I made was reconnecting the temperature probe, since they'd disconnected them - I assume to test. It seems suspicious that so many units are failed/bad, but I have no idea how sturdy these units are, or if they are mis-wired somewhere.

From watching the last attempt at getting it to work, the controller was originally directly hooked up to the transformer in the 3rd picture instead of of the r/w terminals, and they tried the solenoid being connected directly to the H terminals without the power line in the loop (which seems like it would never work?). Hopefully there's something trivial I'm missing.

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Last edited by PJmax; 01-18-18 at 11:09 AM. Reason: reoriented/enhanced pictures
Old 01-18-18, 10:08 AM
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A little confused, so the solenoid does not open ? What sensors are you talking about ? Temperature probe ?
Old 01-18-18, 10:10 AM
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Yes, the temperature probe - the new controller came with one so I replaced it and verified the resistance was correct.
The solenoid does open if I jump H-H. It does not open if I put the controller in test mode.
Old 01-18-18, 11:22 AM
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The temperature sensor goes outside. It's the ODT sensor. It changes the humidity level automatically based on outside temperature changes.

Fairly certain it's wired wrong.
I need help with IDing the wiring. The pictures are good. A wider shot of the furnace board would be helpful.

There is an 8 conductor cable from the hstat to the furnace.
brown & orange for ODT (sensor)
blue on W at hstat and W1 at furnace
yellow not used
green on Gf at hstat and G at furnace
black on G at hstat and YLO at furnace ???? That doesn't look right.
red and white..... VERY important.... make sure these two wires are indeed the ones that go to that transformer.

The humidistat needs a C connection to the furnace board. Right now you don't have one.

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