How do I troubleshoot a blank display on the RTH5160?
If the display is blank, ensure that fresh AA alkaline batteries are properly installed in the back of the thermostat. The batteries are required to power both the display and all operations of the thermostat. If the display remains blank after checking the batteries, contact Honeywell Customer Care at 1-800-468-1502.
From the official Honeywell Set Temp RTH5160 Thermostat manual, page 14
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