Fan Switch doesn't work on setting 1,2 or 3 and only on setting 4.

[probedude]

Could be the same thing.  Only position 4 powers the blower motor directly,
bypassing this power resistor.
At position 1, you are going through resistor 1, 2, and 3.  In position 2
you are going through 2 and 3.
And finally in position 3 you are only going through 1 resistor.

You could just have an open resistor #2 that is preventing you from using
setting 1 and 2.

Pull the resistor assembly and perform a continuity test.

Dave