Rear blower smoke

'99 T&C... during the summer I turned on the rear blower for the air conditioning once and when I parked there was smoke (not steam) coming from the driver's side rear wheel well. I've used both the a/c and heat with only the front blower on since then with no problem. I rarely drive the van but I might have to start using it regularly soon so I'd like to see what I can do about this problem. Any advice is greatly appreciated.