Question about Aprilaire 400 Humidifier

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Constant Red Light on Control Panel Circuit Board

Humidifier now does not work. The reset does not work. However there is now a constant red light illuminated on the circuit board within the humidistat housing.
Note - a cpmplete new HVAC system was recently installed.

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Re: Constant Red Light on Control Panel Circuit Board

The red light under the cover of the humidistat is fault light. This light typically indicates that there is an issue with your connection at the two wiring terminals labeled ODT on the humidistat. I would recommend checking to confirm that there is something currently connected to the two terminals. As a side note these two terminals can not be jumped out with a jumper, and must utilize either the outdoor temperature sensor (part 8052) or the manual mode resistor (part 4336).

Posted on Apr 23, 2010

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You can get parts from the link below:

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We appreciate the opportunity to be of assistance.

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Technical Support
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