Offhand I don't see it as a motor problem because it runs at lower speeds. I'd first try to get it to run on high speed. That way there are no resistors being used. I assume you have an air conditioning car because of your mention of the in-line fuse. This exists on the A/C cars only.
1, With a meter check that you have 12 volts to ground coming into the relay connector input power. Check this on the wire with the in-line fuse in it. Believe this is a large orange wire. This is the power for the fan in high speed.
2, With a meter check that you have 12 volts to ground coming into the relay connector coil input wire. Believe this is a blue wire. The switch should be selected to high. This is the power for the relay coil that closes the relay. This 12 volts comes from the switch and not from the in-line fuse.
The purple wire on the relay is the output to the fan motor. When the relay coil wire is energized by the switch, the relay closes and puts 12 volts from the in-line fuse wire to the purple wire.
This should get you started.
1, With a meter check that you have 12 volts to ground coming into the relay connector input power. Check this on the wire with the in-line fuse in it. Believe this is a large orange wire. This is the power for the fan in high speed.
2, With a meter check that you have 12 volts to ground coming into the relay connector coil input wire. Believe this is a blue wire. The switch should be selected to high. This is the power for the relay coil that closes the relay. This 12 volts comes from the switch and not from the in-line fuse.
The purple wire on the relay is the output to the fan motor. When the relay coil wire is energized by the switch, the relay closes and puts 12 volts from the in-line fuse wire to the purple wire.
This should get you started.