My gas was turned off for a day for work in the neighborhood. When service was restored the furnace would not come on. When the thermostat is set for the fan to be "on" the fan will blow fine. Once the I set it to "heat" the blower shuts off and the status light blinks 3 times. I can't find something that will tell me what that means for this model number. I have found some similar that says it's a pressure switch problem. Is this correct?