electrical wiring,Blower Motor only working on highest speed.

My fan only works on the highest setting. It is a manual system. I went and bought a new blower motor resistor and thought that would be the fix. When I took the old part out of the connector , I did notice some corrosion/ burn damage. Here's where it gets tricky. I accidentally installed the blower motor resistor upside down. However, the fan started working, just in a backwards sort of manner. Setting 1 now blows a level 3 power. Setting 2 still blows a level 2 power. Setting 3 blows a level 1 power. Setting 4 still blows a level 4. I started to smell something. Took the blower resistor