Test of system finds heating not kicking. Trace of system finds all wires correct and no wiring problems. This confirms the Nest thermostat is bad. Installed new Honeywell Wi-Fi Programmable comparable to the Nest (in my opinion better). Tested fan, cooling, and heating for correct wiring operation. All okay at this time. 5 Year Honeywell Parts Warranty 1 Year Residential Experts Labor Warranty