Where do you start with a 2000 Mercury Marquis when the fan motor doesnt blow but the AC is working you can hear it cycling undr the hood but no forced air What do you do?

Take a 12 volt tester ( $ 4.00) and test for 12 volts right at the blower motor. If there is 12 volts at the motor then your blower motor is bad. If no power then trace it back. Some models have a blower motor resistor; some have relays .Have your Ford dealers parts department print you out a picture of these parts which will identify their locations.