4 possibilities,
A) Track pad or keyboard cable is damaged.
B) sometimes corrupted bios can cause this.
C) download the schematics if you can and look for the thermal sensors.
D) I/O board problem. check the cable and then the board itself.(Camera sensor is there too)
E) SMC, try ultrasonic cleaning or replacing the chip if you are sure thats the problem.
I have question from you, when you connect the charger does it charge the battery? it is very important. and If it does, what is the color of the magsafe.(Green and then orange?)
WinMac Inc.('''MacBook Repair Centre''')
[http://WinMac.ca|WinMac.ca]