Having problems with heater on a bryant model:gb1hav048111. Just replaced thermostat thinking that would be the problem for it. Unit turns on by its self but come to find out you can remove the thermostat and still turns on can even remove the thermostat wires to the motherboard and still comes on. The heater has problems igniting first time it ignited the cuts off fast then fan runs for a little bit then ignited it right stays lit and temp seems to rise. A switch on the wall that kills the power to the unit so turning it on and off with the switch instead of the thermostat. I just wanted to know if I need a new motherboard or something else to make it work wright