"But, the motor doesn't do anything when I step on the pedal."
Plug the motor plug directly into a wall outlet after removing the needle and raising the presser foot. If it runs the problem is in the foot control and wires. If it doesn't run, the motor needs to be tested and repaired.
90% of motors that are thrown away are good. Usually they need oil, like straight weight 30 SAE, non-detergent type car motor oil.
Only add two drops of oil to any oiling holes in the end covers. Work the oil in by turning the motor by hand.
Foot controls are not that complicated. If they are the wound NICHROME wire type, you can measure the resistance of the wire. The resistance of the entire length of the wound wire is usually about 90-100 ohms total using a VOM. If it's infinity, the Nichrome spiral wire is broken or a contact is bad at some point. Make sure you have 125VAC power across the two lamp cord wires from the wall outlet or check the wire continuity.
Make sure the wiper arm inside makes contact with any rivet taps along the wound wire using a good Volt-Ohm-Meter, VOM.
Check that the motor/light box inside to see if a spot welded copper wire on a bent blade is detached. If detached, cut a slot with a Dremel tool cutoff blade and put the wire in that slot. Then solder it in place.
Check the lampcord wall plug for loose or broken wires.
You can test the motor outlet and light outlet with a light bulb. Press on the foot control and the bulb in the motor outlet should be dim and get brighter as you press harder.
You could have bad motor brushes also. If they are bad, get new ones at a sewing supplier.
If you don't know how to test electronics, get someone that can do it like a Ham Radio Operator in your neighborhood. Look for a radio antenna tower. Ring the door bell. Ask for help.
Reasons a motor won't work.
1. The motor winding is cooked and looks blackened. Terminal or unsafe.
2. Bearings are full of oxidized oil that is now sticky. Oil it. Try liquid wrench on the bearing and shaft, not in the oiling holes.
3. Brushes are oxidized and/or don't make contact.
4. Armature is very loose end-to-end, or is loose up and down. It needs new bronze sleeve or ball bearings.
CAUTION!!! If the motor is seized, pressing the foot control or plugging it directly into a wall outlet will send the current through the winding to infinity and that's not good. A stalled motor is a dead short, electrically. During any quick plug-in power test, a stall and buzz means disconnect NOW!
Heavy current will bake the motor winding brown or black. Copper color with shellac is fine but black is not good.
Stefan