Upon arrival found that the system wasn’t heating. Checked inside air handler and found everything ok. Checked Tstat and found that the W wire wasn’t connected. Connected wire and Tstat would say that it lost power. Disconnected wire and Tstat still said it had no power. Checked incoming 24v to Tstat and it was present. Checked continuity through wires and every was good. Manually turned on system and heat strips were coming on. System has a bad nest thermostat that need to be replaced. Also found that the disconnect outside has been straight wired through which is not code. Disconnect will need to be replaced. Found that the contactor was pitted pretty bad and the capacitor was reading 38/60mfd which is bad. Emailed estimate over to to make repairs.