Can anyone tell me what might I check to determine why my heat/air conditioning blower only works in the last (highest ) switch position?

 

not sure if the rams have them, but i know the dakotas have a blower resistor that goes bad and does that.

 

Yea they have resistors and it happened on my cousins cummins and that was the cause, should be in fresh air tube under dash

 

might be the selector switch

 

heres what your gonna do...underneath the passenger side of the dash you'll see the blower. there should be a connector going into the housing. take off the connector and remove the the screws holding the resistor into the housing. Now sniff it or look for any noticable things wrong. If it smells burnt or looks like somthin is wrong replace it thats ur issue.