I have an Aprilaire 600 whole house humidifier controlled by Honeywell PC8900 thermostat. For a while now the PC8900 has been showing "Humid--%", which according to the Owners Manual means that I have a humidity sensor failure.
Is this a sensor inside of the PC8900? If so, is it something that can be replaced or do I just need to order a new thermostat?
Could any indirect reason (i.e. solenoid valve failure) cause this error message.
Appreciate any input