'98 model whirling noise with power door locks?

I just recently traded for this van and when the power door locks engage or release MOST of the time, I hear a whirling noise that is definitely associated with the locks. Has anyone else had this problem and know of a solution?

I own a 96 T&C mini-van, that when I purchased it, it had a similar noise from the passenger side sliding door. Problem also was that the door could not be locked. Being a locksmith, I investigated the locking problem, and found the electric solenoid unit was making the noise, do to a cracked internal gear drive mechanism. There is a small motor, driving a gear inside the unit, that was spinning a causing the whirling sound. Replacement of the solenoid unit solved my problem. Hope this helps.

Where is the electric solenoid unit located? Do you have a part number?