I have an electrical hvac unit. Handler is in the attic, and I have an outside unit. My unit has 2 zones. The units are 6 years old, I have already replaced the outside unit and the capacitor in the attic air handler. If I place the thermostat upstairs on heat and set it to 70 and have it on auto, it won't cut off...it will be 80 degrees upstairs. If i set the downstairs thermostat to auto, heat and 70 it will be 80 degrees downstairs and 85 degrees upstairs. Any other info anyone needs? I look forward to responses.
Do you have a volt meter? If so check at the air handler and see if a control is telling the heat to run or if a sequencer is stuck. Voltage at W and C on at the air handler would mean the thermostat or zone control is telling the elements to run.