If the behavior is the same after replacement, I would also look into your keyboard cable. As I'm sure you noted when you did the fan replacement, the fans actually connect to the keyboard's board, not the logic board. The cable which then connects this board to the logic board carries signals for both the fan and the keyboard. Apple tapes over the connector on the keyboard end, but it's possible this cable is bad, has come loose, or something to that effect.
Otherwise I would make sure the fan connector itself is sound, and the little locking latch is in place.
If not those, then it's very possible it's a logic board issues.
[image|2740755]