Troubleshooting Nest thermostat Rc (red) wire issue- no power detected problem. Fuse fix. - YouTube
Nest Thermostat No Power To RC Wire (E73 Error): How To Fix - HowTL
Thermostats 24 Volt Transformer C Wire Power Adapter for Nest, Ecobee, Honeywell WiFi Thermostats, Power Supply for Nest Hello, Ring Smart Doorbells Chime - Amazon.com
Help! Nest says "no power to Rh" and "no power to Rc" but old tstat works fine : r/Nest