When heat setting on my thermostat is in off position the heater still continues to heat the house to 78 . When I open the doors and windows at night it will drop?But in the day it typically has been warmer inside the house than the outside temp?

Thermostat off for three to four days now but heater keeps house at 78. When I come home at night open doors and windows temp drops by morning to70-71 degrees . But when I leave house and come home temp is back at 78 degrees?

Turn off the breaker to your heater and see if that makes a difference. If you have poor insulation in your attic, a sunny day can easily raise the temperature of your home. Without an experienced hvac tech looking at your system there is no way to tell what is going on. It could be a bad thermostat, bad wiring, bad control board.. etc.