Product review (4 stars): My original humidistat started to go bad after 4-5 years
My original humidistat started to go bad after 4-5 years, and after a technician tried to charge me $300 to replace it, I decided to do it myself.  Pop the cover off, remove four screws and reconnect two wires, and 10 minutes later I was good to go.

Giving it 4 stars because like the other Aprilaire components (especially the solenoid valve), these parts should last much longer than they do.