take out the blower motor, there is one screw and turn it to counterclockwise and the whole housing with the motor pops out. Once done with that hook 12v directly to the blower motor, if it doesn't work then the motor itself is gone. most common cause is a bad ground in the motor, but its a sealed can motor so its just easier to go get a new one. if it does work just start using a volt meter and just start probing wires. turn the switch on so that it should work and probe the connector to the motor and see if you get a voltage.
it won't be the resistor pack, if the resistor pack went then the motor would work only on high, but it would work.
the fuse is a quick check, there is also one under the dashboard on the driver's side footwell i want to say it is fuse number 30 or 32, check that... its very rare for the switch to go bad unless there is a short or a power surge and it fried the fuses.
there has been some extreme cases where the wiring going into and out of the internal fuse panel has melted but its rare, you can also find a thread where someone took apart the fuse panel and cleaned it and such...
i recommend checking the fuses first then removing the blower motor and hooking it up to 12v first... the most common things to go and the easiest to fix.
1999 Contour SE, Zetec 4cly. CAI with stock air box, velocity stacks on CAI, optimized HP exhaust headers.
Goal: HP somewhere around 175-225. Stock look. Nice interior.