Thank you for contacting us. Does your humidistat have a blower activation switch on the lower left hand side of the humidistat? If you do it is our #60 humidistat, and if it is not there you have a #58 humidistat. The R & C are the two connections that supply power to the humidistat to give you the numbers on the digital display. The 60 you wire right into the R & C off the furnace panel. The 58 you need a constant 24 volt and 10 VA power source which you could get by using the transformer off a constant 120 volt power source to power the humidstat. If you are doing this correctly and you still do not get the numbers to show up, then you have a bad humidistat and you need to go back to where you purchased it from and exchange it under warranty provided you used a certified HVAC contractor to do the installation. Our warranty is only valid if you used a certified HVAC contractor to do the installation. If you have any additional questions please contact us at 800-334-6011.

Thank you

www.aprilaire.com

Kevin Engen
Customer Service
Research Products Corporation