Hello my name is XXXXX XXXXX will be my pleasure to assist you. The problem is the fan limit in the furnace . If the thermostat is set to manual it will come on because the power is sent directly to the blower motor. It won't come on for heat because the power has to go through the heat sensor in order for the blower to come on it has to reach a certain temperature before kicking on the blower.
Furnace goes on but blower doesn't unles I put the fan swithc on manual.