Climate control works on High only

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:frown: 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? :frown:

I would guess a blower motor resistor on my 96 Dakota its locater on firewall on passenger side, not sure about 04, here's what it looks like:
http://info.rockauto.com/SMP/SMPDetail3.html?RU95.html

I had the exact ssme thing happen on my 03' and after trying several diffrent things it came down to this http://cgi.ebay.com/ebaymotors/AC-Heater-Blower-Motor-Resistor-Dodge-Dakota-01-04-NEW_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1205Q7c66Q3a2 Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a1Q7c293Q3 a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZitem 130285869184QQitemZ130285869184QQptZMotorsQ5fCarQ5 fTruckQ5fPartsQ5fAccessories
i wish i would have known in the begining because it takes all of 15 min to change
and if you find a leak under the passenger side carpet IT IS NOT THE HEATER COIL! DO NOT TAKE YOUR DASH APART! you will find that the drain hose on the passenger side firewall is behind a heat shield and it tends to blow back in on the outside of that hose, just bend out the heat shield a little and coat arount that hose with some 5200 sealant it should save you a couple of days trying to get the dash out to get to everything else