2003 Caravan Heater & A/C on works on Highest Setting

My heater or A/C will only operate on the highest blower setting in my 2003 Dodge Caravan.

I've check the fuses and they're all good. Is it a relay or the motor?

I've seen this question dozens of times on google searches but I've never seen this question answered. If this problem is so widespread among Dodge vehicles from 1998 through the 2004 models why isn't there more information on the subject?

Thanks for your responses in advance.