When I turn on the heater it works for some time 5-15 until 65-67F then it shuts off. Cool air is blowing. To restart I have to swithch off and switch on the heater (it works if I switch off and switch on t-stat as well). I set 63F last nights, and it worked just fine through the night. In the morning, I set 72 and soon the heater (burning) shut off. Simple LED flashed "system lockout" fault.
Any suggestions?
Thanks.