Trane AC heating unit stopped runningbut the breaker not blown and was cooling just fine then appeared to be no power to thermostat?

Answer 1

The first thing you check is your low voltage, you have a transformer inside the unit near the electrical panel or relays. Check transformer high side and low side, you should have 24 volts. Got to thermostat and check wiring your red wire should have 24 volts as well fed from your transformer. Another way is if you have the red wire connected to your yellow wire at the thermostat after you remove the thermostat you will see the wires i am talking about. Connect them together ans see if your unit comes on. If it does replace your thermostat. Hope this helps. Mysterio619j.