I guess no one is manning up with a response because this is probably the most frequently written about subject. A search would yield more information than you need. The short answer however is that you probably have a bad regulator. It is attached to a porcupine-like heat sink directly under the blower motor. So the good news is that you already know how to get to it because you replaced the blower motor a couple of years ago. Personally, I would never buy a new one and would rather just pick up one or two at the boneyard for a half a hundred for the pair and put one on the shelf. 
