my central heat comes on in summer when it gets above 90 outside and will not shut off until temp cools down?
maybe it is your a/c and not your heater that is coming on? sorry for the thought but heaters do not come on about 90 degrees. they do not even have a setting for that... wish you well. ps make sure the heat switch is off and finally do you have a separate a/c unit than your heating unit... your heater will come on if the a/c unit tells the heater is below temp.
Do you have a heat pump? Its possible that the reversing valve is stuck in heat mode. Or, if you have just installed a thermostat reciently the hot and cold wires might be reversed as well.
furnaces have a thermostatic fan control that turns the blower on when the heat exchanger gets above a certain temp. (usually adjustable from 90-110 degrees) if you don't want it to come on you can aways unplug the furnace or turn off the switch that powers it. just don't forget to turn it back on when it gets cold.
