[pete galati]

Hi my name is pete I have a old york gas furnace not the newer type with the circuit board I need a wiring diagram for a typical york gas furnace.I installed a new blower motor and thermostat,new gas valve and cleaned all components.gas ignites but blower won't come on if thermostat is on auto but it does come on when set to on.also new limit switch .I really need a wiring diagram for this thing.it is an old type of gas furnace

[labman]

There shouldn't be that much to it. The red wire from the transformer should go to the limit switch, and then to a relay. Another terminal on the relay will go back to the transformer. When the limit switch heats up, it closes sending power through the relay coil. That closes the contacts between the line from the house and the lead to the blower turning the blower on. Relays are notorious problem causers. Fortunately, on older furnaces, they are cheap and easy to check and replace. Follow the lead from the blower back to a little box with 4 wires.

[NorthernHeat]

Replace the fan limit control. It is a dial looking device in most cases. When the heat exchanger warms up, it senses the heat and turnson the blower.