Quicksilver Fans Not Working?

G4 Dual 1.0 gHz. The other day I heard a pop, then smelled something electrical. G4 continued to work, but after a short while, it kept on going to sleep. I noticed, that I did not hear the normally loud fans and noticed the fans were not working, both large and small. I figured it was an over heating problem.

I let the machine cool down, then opened it up and directed a large fan to blow air inside, and it works fine. Temp Monitor reads

48.6º C.

Is it likely the fans themselves, a sensor, or the logic board?