MacBook Fan Starting and Stopping constantly

Hi, My daughter has a macbook that has had 3 fan replaced within a month. The fan will cycle on and off constantly. It only stays on for about a second then off then back on... It’s an ongoing process.
Each time I bring it into the GeniusBar they hook it up and run diagnostics on it. They always find that the fan is bad. They replace it (taking a week each time). I come pick it up, bring it home and the fan does the same exact thing. What is wrong with it?
When I picked it up in the store I stood there and let it run for 10 minutes. The fan was fine...I bring it home and now its freaking out again.

I'd have to assume they did an SMC reset there - but you could give that a try. Link

I am having the same problem. Been pulling my hair out about this for weeks now. The fan starts revving at high RPM's randomly on and off for like 3 sec intervals. Sometimes 10-15 secs. Im doing nothing or next to nothing when this happens. Activity monitor says i'm only using like 9% or less of my CPU.

I've had my logic and fan replaced. I've formatted my hd and reinstalled SL. I've reset the pram and the SMC dozens of times. Also checked to see that there is nothing blocking the fan. I took out my battery for a while to see if that had anything to do with it. Didn't think it would but i bought a 3rd party one recently and it works great but its a generic copy. Taking it out didnt seem to help.

Problem went away for a few days after format and install but then comes back which made me think its possibly software, maybe 10.6.8 updater doesn't like one of my 3rd party apps or something like that.

Even more confusing because it happens when i am booted to the install disk so it sounds like hardware, but that seems unlikely because i've changed the fan itself and the logic board.

I'm completely stumped.