Electric Fan Problem

I have a 2002 T&C and one of the electric fans (the one on the driver side) turns on by itself hours after the van has shut off. This has now happened twice that I know of. The first time it happened the van had been setting cold for about 24 hours! Any thoughts on this would be greatly appreciated.

PS: My transmisson had to be replaced at 46,000 miles and the problem started after the replacement. Maybe a connection? Thanks.