Upon arrival for a callback on a 2014 York furnace, found unit not kicking on. This was due to thermostat being stuck in a loop in waiting cycle. I was able to jump at the thermostat and at unit to get unit to come on. I replaced thermostat and same issue was occurring. I pulled common wire and system cycled fine. Common wire is back feeding power or broke. Also just cut common wire out as new thermostat can run without and the old thermostat can not. System operating as intended upon departure.