I have 04 dakota Quad cab V8 . My climate control works on high only. Changed with one I bought from internet. I put it in, same thing High only. what are the odds. Does the blower have three speeds? I took blower

off unpluged connector and checked voltage . All four speeds register 12 Volts DC. I did find another set of wires with connector beside fan. two of the four wires had corrosion green just like a battery post woud do. is this connector have to do with the low med & high not working?