Arrived to remedy an inoperable humidifier. Upon inspection of the humidifier found a red light indicating that the steam canister is not filling with water. Performed diagnostic on the unit and determined that the solenoid valve or fill valve is not allowing water to flow properly. Called Aprilaire tech-support to verify my diagnosis and start the warranty process. Spoke with homeowner about the necessary repair. With homeowners approval performed the replacement of the fill valve. Tested system operations. System is functioning properly at this time.